英语词源字典 - 在线词源网站

irradiance (adj.)[irradiance 词源字典]: 1660s, from irradiant (1520s), from Latin irradiantem (nominative irradians), present participle of irradiare (see irradiate). Related: Irradiancy (1640s).[irradiance etymology, irradiance origin, 英语词源]
irradiate (v.): c. 1600, "to cast beams of light upon," from Latin irradiatus, past participle of irradiare "shine forth," from assimilated form of in- "into, in" (see in- (2)) + radiare "to shine" (see radiate). Meaning "expose to radiation other than light" (originally X-rays) is from 1901. Related: Irradiated; irradiating.
irradiation (n.): 1580s, from French irradiation, from Latin *irradiationem, noun of action from past participle stem of irradiare (see irradiate). Originally of light (literally and figuratively); of X-rays, etc., from 1901.
irradicable (adj.): 1728, from ir- "not" + radicable.
irrational (adj.): late 15c., "not endowed with reason" (of beats, etc.); earlier (of quantities) "inexpressible in ordinary numbers" (late 14c.); from Latin irrationalis "without reason," from assimilated form of in- "not, opposite of" (see in- (1)) + rationalis "reason" (see rational). Meaning "illogical, absurd" is attested from 1640s. Related: Irrationally.
irrationality (n.): 1560s, from irrational + -ity.
irreconcilable (adj.): 1590s, from French irréconcilable (16c.), from Medieval Latin *irreconcilabilis, from assimilated form of in- "not, opposite of" (see in- (1)) + reconcilabilis (see reconcile). Related: Irreconcilably. As a noun from 1748.
irrecoverable (adj.): mid-15c., from Old French irrecovrable, from assimilated form of in- "not, opposite of" (see in- (1)) + recovrable (see recover). In same sense irrecuperable (from Late Latin irrecuperabilis) is from mid-14c. Related: Irrecoverably.
irredeemable (adj.): c. 1600, from assimilated form of in- (1) "not, opposite of" + redeemable. Related: Irredeemably.
irredentist (n.): 1882, member of Italian political party which (after 1878) demanded the annexation of neighboring Italian-speaking regions (Trieste, S. Tyrol, Nice, Corsica, etc.), from Italian Irredentista, from (Italia) irredenta "unredeemed (Italy)." Related: Irredentism.
irreducible (adj.): 1530s, from assimilated form of in- (1) "not, opposite of" + reducible. Related: Irreducibly; irreducibility.
irrefragable (adj.): "that cannot be refuted," 1530s, from Late Latin irrefragabilis, from assimilated form of in- "not, opposite of" (see in- (1)) + Latin refragari "to oppose, contest," from re- "back" (see re-) + frag-, base of frangere "to break" (see fraction). Related: irrefragably; irrefragability.
irrefrangible (adj.): c. 1719, "that cannot be broken," from assimilated form of in- "not, opposite of" (see in- (1)) + refrangible.
irrefutable (adj.): 1610s, from Latin irrefutabilis "irrefutable," from assimilated form of in- "not, opposite of" (see in- (1)) + refutabilis, from refutare (see refute). Related: Irrefutably; irrefutability.
irregardless: an erroneous word that, etymologically, means the 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 colloquial use of the double negative as an emphatic.
irregular (adj.): late 14c., "not in conformity with Church rules," from Old French irreguler (13c., Modern French irrégulier), from Medieval Latin irregularis, from assimilated form of in- "not, opposite of" (see in- (1)) + Latin regularis (see regular (adj.)). General sense is from late 15c.
irregular (n.): "a soldier not of the regular army," 1747, from irregular (adj.).
irregularity (n.): early 14c., "violation of Church rules," from Old French irregularité (14c.) and directly from Medieval Latin irregularitas, from irregularis (see irregular). Meaning "state of being not regular" is from 1590s.
irrelevance (n.): 1735, from irrelevant + -ance. Earlier in the same sense was irrelevancy (1590s).
irrelevant (adj.): 1680s, from assimilated form of in- (1) "not, opposite of" + relevant. Related: Irrelevantly.