A- (3) prefix meaning "not," from Gk a-, an- "not," from pie base *ne "not" (see un-)

introit --- 1481, from O.Fr. introit (14c.), lit. "a going in," from L. introitus, pp. of introire "to enter," from intro- + ire "to go."

introspection --- 1677, from L. introspectionem, from introspectus, pp. of introspicere "to look into, look at," from intro- "inward" + specere "to look at" (see scope (1)). Introspective is from 1820.

introvert (v.) --- 1654 (implied in introversion), from L. intro- "inward" + vertere "to turn" (see versus). Introverted (adj.) is from 1781. The noun (opposed to extrovert) is 1918, from Ger. psychology, introduced there by C.G. Jung (1875-1961).

intrusion --- c.1387, from O.Fr. intrusion, from M.L. intrusionem (nom. intrusio) "a thrusting in," from L. intrusus, pp. of intrudere, from in- "in" + trudere "to thrust, push" (see extrusion). Intrude is first recorded 1534.

intuition --- 1497, from M.Fr. intuition, from L.L. intuitionem (nom. intuitio) "a looking at, consideration," from L. intuitus, pp. of intueri "look at, consider," from in- "at, on" + tueri "to look at, watch over" (see tuition). The verb intuit is an 1840 back-formation apparently coined by De Quincey.

inundation --- 1432, from L. inundationem (nom. inundatio) "an overflowing," from inundatus, pp. of inundare "to overflow," from in- "onto" + undare "to flow," from unda "wave" (see water).

inure --- c.1420, in ure "in practice," from obsolete ure "work, practice, exercise, use," probably from O.Fr. uevre, oeuvre "work," from L. opera (see opus).

invalid (adj.) --- 1635, "not strong, infirm," also "of no legal force," from L. invalidus "not strong, infirm, weak, feeble," from in- "not" + validus "strong." Meaning "infirm from sickness, disease, or injury" is from 1642. The noun is first recorded 1704, originally of disabled military men. Invalidate is from 1649. Invalides is short for Fr. Hôtel des Invalides, home for old and disabled soldiers in Paris.

invaluable --- 1576, from in- "not" + value "estimate the worth of" + -able.

invariable --- 1607, from in- "not" + variable.

invasion --- 1439, from M.Fr. invasion (12c.), from L.L. invasionem (nom. invasio) "an attack, invasion," from L. invasus, pp. of invadere "go into, fall upon, attack, invade," from in- "in" + vadere "go, walk" (see vamoose). Invade is 1491, from invadere.

invective (n.) --- 1523, from a M.E. adj. (1430), "characterized by denunciatory language," from L.L. invectivus "abusive," from L. invectus, pp. of invehi "to attack with words" (see inveigh). For nuances of usage, see humor.

inveigh --- 1486, "to introduce," from L. invehi "to attack with words," originally "carry oneself against," from passive inf. of invehere "bring in, carry in," from in- "against" + vehere "to carry" (see vehicle). Meaning "to give vent to violent denunciation" is from 1529.

inveigle --- 1494, "to blind (someone's) judgment," from M.Fr. aveugler "delude, make blind," from V.L. *aboculus "without sight, blind," from L. ab- "without" + oculus "eye." Loan-transl. of Gk. ap ommaton "without eyes." Meaning "to win over by deceit, seduce" is c.1540.

invention --- c.1350, from L. inventionem (nom. inventio) "a finding, discovery," from inventus, pp. of invenire "devise, discover, find," from in- "in, on" + venire "to come" (see venue). Meaning of "thing invented" is first recorded 1513. Invent is from c.1475. Etymological sense preserved in Invention of the Cross, Church festival (May 3) celebrating the reputed finding of the Cross of the Crucifixion by Helena, mother of Constantine, in 326 C.E.

inventory (n.) --- 1415, from M.Fr. inventaire "detailed list of goods," from M.L. inventorium "list of what is found," from L. inventus, pp. of invenire "to find" (see invention). The verb is first recorded 1601.

inverse --- 1440, from L. inversus, pp. of invertere (see invert).

invert --- 1533, from M.Fr. invertir, from L. invertere "turn upside down, turn about," from in- "in, on" + vertere "to turn" see versus). Inversion is from 1551.

invertebrate (n.) --- 1826, coined from L. in- "not" + vertebra "joint." Invertebrata as a biological classification was coined 1805 by Cuvier.

invest --- 1387 (implied in investiture), "to clothe in the official robes of an office," from L. investire "to clothe in, cover, surround," from in "in, into" + vestire "to dress, clothe" (see wear). The meaning "use money to produce profit" first attested 1613 in connection with the East Indies trade, and is probably a borrowing of It. investire (13c.) from the same L. root, via the notion of giving one's capital a new form. The military meaning "to besiege" is from 1600.

investigation --- 1436, from L. investigationem (nom. investigatio) "a searching into," from investigatus, pp. of investigare, from in- "in" + vestigare "to track, trace," from vestigium "footprint, track" (see vestige). Investigate is c.1510 back-formation.

inveterate --- 1528, from L. inveteratus "of long standing, chronic," pp. of inveterare "become old in," from in- "in, into" + veterare "to make old," from vetus (gen. veteris) "old" (see veteran).

invidious --- 1606, from L. invidiosus "envious," from invidia "ill will" (see envy).

invigorate --- 1646, from L. *invigorare, from in- "not" + vigorare (see vigorous).

invincible --- 1412, from L. invincibilis "unconquerable," from in- "not" + vincibilis "conquerable."

inviolable --- 1530, from L. inviolabilis "invulnerable," from in- "not" + violabilis, from violare "to do violence to" (see violation). The adj. inviolate "unbroken, intact" is attested from 1412.

invisible --- 1340, from O.Fr. invisible (13c.), from L. invisibilis "unseen, invisible," from in- "not" + visibilis (see visible).

invitation --- c.1445, from L. invitationem (nom. invitatio) "invitation," from invitatus, pp. of invitare "invite, treat, entertain," originally "be pleasant toward," from in- "toward," second element obscure, one suggestion is a lost word *vitus "pleasant." Meaning "the spoken or written form in which a person is invited" is from 1615. Invite (v.) is a 1533 back-formation; as a noun variant of invitation it is attested from 1659.

invocation --- c.1375, from O.Fr. invocation (12c.), from L. invocationem, noun of action from invocare (see invoke).

invoice --- 1560, from M.Fr. envois, pl. of envoi "dispatch (of goods)," lit. "a sending," from envoyer "to send" (see envoy).

invoke --- 1490, from M.Fr. envoquer (12c.), from L. invocare "call upon, implore," from in- "upon" + vocare "to call," related to vox (gen. vocis) "voice" (see voice).

involuntary --- 1531, from L.L. involuntarius "involuntary," from in- "not" + L. voluntarius (see voluntary).

involve --- 1382, from L. involvere "entangle, envelop," lit. "roll into," from in- "in" + volvere "to roll" (see vulva). Originally "envelop, surround," sense of "take in, include" first recorded 1605. Involved "complicated" is from 1643.

invulnerable --- 1595, from L. invulnerabilis, from in- "not" + vulnerabilis (see vulnerable).

inward --- O.E. inneweard, from P.Gmc. *inwarth "inward" (cf. O.N. innanverðr, O.H.G. inwart, M.Du. inwaert), from root of O.E. inne "in" + -weard (see -ward).

inwit --- M.E. word meaning "conscience" (c.1225), "reason, intellect" (c.1305), from in (adv.) + wit (n.). Not related to O.E. inwit, which meant "deceit." Joyce's use in "Ulysses" (1922), which echoes the 14c. work "Ayenbite of Inwyt," is perhaps the best-known example of the modern use of the word as a conscious archaism.

iodine --- 1814, formed by British chemist Sir Humphry Davy from Fr. iode "iodine," coined 1812 by Fr. chemist Joseph Louis Gay-Lussac from Gk. ioeides "violet-colored," from ion "violet" + eidos "appearance" (see -oid). So called from the color of the vapor given off when the crystals are heated.

ion --- 1834, introduced by Eng. physicist and chemist Michael Faraday (suggested by William Whewell), coined from Gk. ion, neut. prp. of ienai "go," from PIE base *ei- "to go, to walk" (cf. Gk. eimi "I go;" L. ire "to go," iter "a way;" O.Ir. ethaim "I go;" Ir. bothar "a road" (from *bou-itro- "cows' way"), Gaulish eimu "we go," Goth. iddja "went," Skt. e'ti "goes," imas "we go," ayanam "a going, way;" Avestan ae'iti "goes;" O.Pers. aitiy "goes;" Lith. eiti "to go;" O.C.S. iti "go;" Bulgarian ida "I go;" Rus. idti "to go"). So called because ions move toward the electrode of opposite charge. Ionosphere coined 1926 by R.A. Watson-Watt.

Ionian --- of Ionia, the districts of ancient Greece inhabited by the Ionians (including Attica and the north coast of the Peloponnesus, but especially the coastal strip of Asia Minor, including the islands of Samos and Chios). The name probably is pre-Gk., perhaps related to Skt. yoni "womb, vulva," and a ref. to goddess-worshipping people. Also used of the sea that lies between Italy and the northern Peloponnesus (1632). The musical Ionian mode (1844) corresponds to our basic major scale but was characterized by the Greeks as soft and effeminate. The Ionic order of Gk. architecture is attested from 1563.

iota --- 1636, figurative use of iota, ninth and smallest letter in the Gk. alphabet, after Matt. v:18 (see jot). The letter name is from Heb. yodh.

Iowa --- state name ult. comes from the native people, of the Chiwere branch of the Aiouan family; said to be from Dakota ayuxba "sleepy ones."

ipecac --- 1788, borrowing via Port. of a shortened form of Tupi ipecacuana (1682), a medicinal plant of Brazil, the Indian word said to mean "small plant causing vomit."

ipse dixit --- 1477, from L., lit. "he (the master) said it," translation of Gk. autos epha, phrase used by disciples of Pythagoras when quoting their master.

ipso facto --- 1548, from L., lit. "by that very fact."

Ira --- masc. proper name, from Heb., lit. "watchful," from stem of 'ur "to awake, to rouse oneself."

Iran --- from Pers. Iran "Persia," from Middle Persian Eran (sahr) "(land) of the Iranians," gen. pl. of Er "an Iranian," from O.Pers. ariya- "compatriot," from PIE aryo-, self-designation of the "Aryan" people (see Aryan). It became the official country name in 1935 under Reza Shah, according to one story on the suggestion of the Persian embassy in Berlin.

Iraq --- country name (1920) is from Arabic name attested since 6c. for the region known in Gk. as Mesopotamia; often said to be from Arabic `araqa, covering notions such as "perspiring, deeply rooted, well-watered," which may reflect the impression the lush river-land made on desert Arabs. But the name may be from, or infl. by, Sumerian Uruk (Biblical Erech), the ancient prominent city in what is now southern Iraq (from Sumerian uru "city").

irascible --- 1398, from Fr. irascible (12c.), from L.L. irascibilis, from L. irasci "grow angry," from ira "anger" (see ire).

irate --- 1838, from L. iratus "angry, enraged, violent, furious," pp. of irasci "grow angry," from ira "anger" (see ire).

ire --- c.1300, from O.Fr. ire (11c.), from L. ira "anger, wrath, rage," from PIE base *eis-, forming various words denoting "passion" cf. Gk. hieros "filled with the divine, holy," oistros "gadfly," originally "thing causing madness;" Skt. esati "drives on," yasati "boils;" Avestan aesma "anger").

Irene --- fem. proper name, from Fr. Irène, from L. Irene, from Gk. Eirene, lit. "peace."

irenic --- 1864, from Gk. eirenikos, from eirene "peace." Irenical "peaceful" is attested from 1660.

Irgun --- militant Zionist organization, 1946, from Mod.Heb., lit. "organization," in full Irgun Zvai Leumi "national military organization."

iridescent --- 1796, coined from L. iris (gen. iridis) "rainbow" (see iris).

iridium --- 1804, Mod.L., coined by its discoverer, Eng. chemist Smithson Tennant (1761-1815) from Gk. iris (gen. iridos) "rainbow;" so called for the varying color of its compounds.

iris --- 1387, "prismatic rock crystal," from L. iris (pl. irides) "iris of the eye, iris plant, rainbow," from Gk. iris (gen. iridos) "a lily, iris of the eye," originally "messenger of the gods," personified as the rainbow. The eye region was so called (1525 in Eng.) for being the colored part.

Irish --- c.1205, Irisce, from stem of O.E. Iras "inhabitant of Ireland," from O.N. irar, ult. from O.Ir. Eriu (acc. Eirinn, Erinn) "Erin," which is from O.Celt. *Iveriu (acc. *Iverionem, abl. *Iverione), perhaps meaning "good land." Meaning "temper, passion" is 1834, Amer.Eng. (first attested in writings of Davy Crockett), from the legendary pugnacity of Irish people. Irish-American is from 1832; Irish coffee is from 1950. Wild Irish (1399) originally were those not under English rule; Black Irish in ref. to those of Mediterranean appearance is from 1888.

irk --- c.1460, irken "be weary of, be disgusted with;" earlier intrans., "to feel weary" (c.1330). Of uncertain origin, perhaps related to O.N. yrkja "work" (from PIE base *werg- "to work;" see urge (v.)), or M.H.G. erken "to disgust." Modern sense of "annoy" is from 1483. An adj., irk "weary, tired" is attested from c.1300 in northern and midlands writing. Modern adj. irksome "bothersome, burdensome" is recorded from 1513.

iron --- O.E. isærn (with M.E. rhotacism of -s-), from P.Gmc. *isarnan (cf. O.S. isarn, O.N. isarn, M.Du. iser, O.H.G. isarn, Ger. Eisen) "holy metal" or "strong metal" (in contrast to softer bronze) probably an early borrowing of Celt. *isarnon (cf. O.Ir. iarn, Welsh haiarn), from PIE *is-(e)ro- "powerful, holy," from PIE *eis "strong" (cf. Skt. isirah "vigorous, strong," Gk. ieros "strong"). The verb meaning "press clothes" (with a heated flat-iron) is first recorded 1680; ironing board is from 1843.

Iron Age --- 1592, originally from Gk. and Roman mythology, the last and worst age of the world; the archaeological sense of "period in which humans used iron tools and weapons" is from 1879.

Iron Cross --- from Ger. das eiserne kreuz, instituted by Frederick Wilhelm III of Prussia, originally for distinguished military service in the wars against Napoleon.

Iron Curtain --- in ref. to the Soviet occupation of Eastern Europe, famously coined by Churchill March 5, 1946, in speech at Westminster College, Fulton, Missouri, but it had been used earlier in this context (e.g. by U.S. bureaucrat Allen W. Dulles at a meeting of the Council on Foreign Relations, Dec. 3, 1945). The fig. sense of "impenetrable barrier" is attested from 1819, and the specific sense of "barrier at the edge of the sphere of influence of the Soviet Union" is recorded from 1920. During World War II, Goebbels used in in Ger. (ein eiserner Vorhang) in the same sense.

ironclad --- (adj.) of warships, 1852, Amer.Eng., from iron + clad. As a noun meaning "iron-clad ship," it is attested from 1862). Of contracts, etc., 1884.

irony --- 1502, from L. ironia, from Gk. eironeia, from eiron "dissembler," perhaps related to eirein "to speak" (see verb). Used in Gk. of affected ignorance, especially that of Socrates. For nuances of usage, see humor.

Iroquois --- 1666, from Fr. (1603); not an Iroquoian word; perhaps from an Algonquian language.

irradiate (v.) --- 1603, "to cast beams of light upon," from L. irradiatus, pp. of irradiare "shine forth," from in- "in" + radiare "to shine" (see radiate). Meaning "expose to radiation other than light" (originally x-rays) is from 1901.

irrational --- c.1470, "not endowed with reason" (of beats, etc.), from L. irrationalis "without reason," from in- "not" + rationalis "reason" (see reason). Meaning "illogical, absurd" is attested from 1641.

Irredentist --- 1882, member of It. political party which (after 1878) demanded the annexation of neighboring It.-speaking regions (Trieste, S. Tyrol, Nice, Corsica, etc.), from It. Irredentista, from (Italia) irredenta "unredeemed (Italy)."

irrefragable --- that cannot be refuted, 1533, from L.L. irrefragabilis, from L. in- "not" + refragari "to oppose, contest," from re- "back" + frag-, base of frangere "to break" (see fraction).

irrefrangible --- c.1719, "that cannot be broken," from in- "not" + refrangible, from re- "back" + L. frangere "to break" (see fraction).

irrefutable --- 1620, from L. irrefutabilis, from in- "not" + refutabilis (see refute).

irregardless --- an erroneous word that, etymologically, means the exact opposite of what it is used to express, attested in non-standard writing from at least 1870s (e.g. "Portsmouth Times," Portsmouth, Ohio, U.S.A., April 11, 1874: "We supported the six successful candidates for Council in the face of a strong opposition. We were led to do so because we believed every man of them would do his whole duty, irregardless of party, and the columns of this paper for one year has [sic] told what is needed."); probably a blend of irrespective and regardless. Perhaps inspired by the double negative used as an emphatic.

irregular --- c.1380, "not in conformity with Church rules," from O.Fr. irreguler (13c.), from M.L. irregularis, from in- "not" + L. regularis (see regular). General sense is from 1483. Military sense of "a soldier not of the regular army" is from 1747.

irreligious --- 1561, from L. irreligiosus, from in- "not" + religiosus (see religion).

irreparable --- 1420, from O.Fr. irréparable (12c.), from L. irreparabilis, from in- "not" + reparabilis "that can be repaired" (see repair).

irrepressible --- 1811, from in- "not" + repressible (see repress). First attested in "Sense and Sensibility."

irresponsible --- 1648, "not legally answerable for conduct or actions," from in- "not" + responsible (q.v.). Meaning "not acting with a sense of responsibility" is from 1681.

irreverence --- c.1340, from L. irreverentia "want of reverence," from irreverens "disrespectful, irreverent," from in- "not" + reverens, prp. of revereri "to stand in awe of" (see revere).

irrevocable --- 1382, from L. irrevocabilis "that cannot be recalled," from in- "not" + revocabilis (see revoke).

irrigate --- 1623, from L. irrigatus, pp. of irrigare "lead water to, refresh," from in- "in" + rigare "to water, to moisten," of uncertain origin, perhaps cognate with O.E. regn "rain."

irritate --- 1531, from L. irritatus, from pp. stem of irritare "excite, provoke." An earlier verb form was irrite (c.1450), from O.Fr. irriter.

Irwin --- O.E. Eoforwine "boar-friend;" often confused with Irving, Irvin, which are from Irvine, Ayrshire, or Irving, Dumfries.

is --- O.E. is, from Gmc. stem *es- (cf. O.H.G., Ger., Goth. ist, O.N. es, er), from PIE *es-ti- (cf. Skt. asti, Gk. esti, L. est, Lith. esti, O.C.S. jesti), from base *es- "to be." O.E. lost the final -t-. See be.

Isaac --- masc. proper name, name of a biblical patriarch, from L.L., from Gk. Isaak, from Heb. Yitzhaq, lit. "he laughs," imperf. of tzahaq "he laughed."

Isabel --- a form of Elizabeth that seems to have developed in Provence. A popular name in Middle Ages; pet forms included Ibb, Libbe, Nibb, Tibb, Bibby, and Ellice. The Sp. form was Isabella, which is attested as a color name ("greyish-yellow") from 1600; the Isabella who gave her name to it has not been identified.

Isaiah --- masc. proper name, name of a biblical prophet, from Heb. Yesha'yah, abbreviated form of Yesha'yahu, lit. "salvation of the Lord," from yesha, yeshua "salvation, deliverance."

Iscariot --- traitor, 1647, from the surname of Judas, betrayer of Jesus, in N.T., from L. Iscariota, from Gk. Iskariotes, said to be from Heb. ishq'riyoth "man of Kerioth" (a place in Palestine).

ischium --- the seat bone, 1646, from L., from Gk. iskhion "hip joint," in pl., "the hips," probably from iskhi "loin," of unknown origin.

-ise --- See -ize.

-ish --- adj. suffix, from O.E. -isc, common Gmc. (cf. O.N. -iskr, Ger. -isch, Goth. -isks), cognate with Gk. dim. suffix -iskos. Colloquially attached to hours to denote approximation, 1916.

ish kabbible --- 1921, "I should worry," of unknown origin, but perhaps derived from Yiddish nisht gefidlt. Popularized and perhaps coined by comedienne Fanny Brice.

Ishihara --- name for the popular type of colorblindness test, 1924, from Jap. ophthalmologist Shinobu Ishihara, who devised it in 1917.

Ishmael --- masc. proper name, biblical son of Abraham and Hagar, from Heb. Yishma'el, lit. "God hears," from yishma, imperf. of shama "he heard." The Arabs claim descent from him. Fig. sense of "an outcast," "whose hand is against every man, and every man's hand against him" is from Gen. xvi.12.

Ishtar --- chief goddess of the Assyrians and Babylonians, counterpart of Phoenician Astarte (q.v.), from Akkad. Ishtar.

Isidore --- masc. proper name, from Fr., from L. Isidorus, from Gk. Isidoros, lit. "gift of Isis," from doron "gift." St. Isidore, archbishop of Seville (600-636) wrote important historical and ecclesiastical works and in 2001 was named patron saint of computers, computer users, and the Internet.

isinglass --- 1528, said to be perversion of Du. huysenblas, lit. "sturgeon bladder," from huysen "sturgeon" + blas "bladder;" so called because the substance was obtained from it.

Islam --- religious system revealed by Muhammad, 1818, from Arabic, lit. "submission" (to the will of God), from root of aslama "he resigned, he surrendered, he submitted," causative conjunction of salima "he was safe," and related to salam "peace." Islamic is attested from 1791. Earlier Eng. names for the faith include Muhammadism (1614) and Ismaelism (1604), which in part is from Ishmaelite, a name formerly given (esp. by Jews) to Arabs, as descendants of Ishmael (q.v.), and in part from Arabic Ismailiy, name of the Shiite sect that after 765 C.E. followed the Imamship through descendants of Ismail (Arabic for Ishmael), eldest son of Jafar, the sixth Imam. The Ismailians were not numerous, but among them were the powerful Fatimid dynasty in Egypt and the Assassins, both of whom loomed large in European imagination.

island --- O.E. igland "island," from ieg "island" (from P.Gmc. *aujo "thing on the water," from PIE *akwa- "water") + land "land." Spelling modified 15c. by association with similar but unrelated isle. An O.E. cognate was ealand "river-land, watered place, meadow by a river."

isle --- c.1290, from O.Fr. ile, earlier isle, from L. insula "island," of uncertain origin, perhaps from fem. of adj. *en-salos "in the sea," from salum "sea." The -s- was restored first in M.Fr., then in Eng. in the late 1500s. Dim. form islet is first recorded 1538, from M.Fr. islette.

-ism --- suffix forming nouns of action, state, condition, doctrine, from Fr. -isme, from L. -isma, from Gk. -isma, from stem of verbs in -izein. Used as an independent word, chiefly disparagingly, from 1680.

isobar --- 1864, coined from Gk. isos "equal," + baros "weight," from barys "heavy" (see grave (adj.)).

isolate (v.) --- 1807, back-formation from isolated (1763), from Fr. isolé "isolated" (1642), from It. isolato, from L. insulatus "made into an island," from insula "island." Isolationist, in ref. to U.S. foreign policy, is attested from 1899; isolationism from 1922.

isometric --- 1840, coined from Gk. isos "equal" + metron "measure" (see meter (2)). Originally a method of using perspective in drawing; the physiological sense relating to muscular action is from 1891, borrowed from Ger. isometrisch (1882). Isomer is an 1866 back-formation; isometrics coined 1962 in Amer.Eng.

isosceles --- 1551, from L.L. isosceles, from Gk. isoskeles "with equal sides," from isos "equal" + skelos "leg" (see scalene).

isotope --- 1913, introduced by British chemist Frederick Soddy (1877-1956) on suggestion of Margaret Todd, from Gk. isos "equal" + topos "place;" so called because despite the different atomic weights, the various forms of an element occupy the same place on the periodic table.

Israel --- O.E., "the Jewish people," from L. Israel, from Gk., from Heb. yisra'el "he that striveth with God" (Gen. xxxii.28), symbolic proper name conferred on Jacob and extended to his descendants, from sara "he fought, contended" + El "God." As an independent Jewish state in the country formerly called Palestine, it is attested from 1948. Citizens of it are called Israelis; the ancient people are Israelites (1382).