"plainly illogical," 1550s, from French absurde (16c.), from Latin absurdus "out of tune, discordant;" figuratively "incongruous, foolish, silly, senseless," from ab- "off, away from," here perhaps an intensive prefix, + surdus "dull, deaf, mute," which is possibly from an imitative PIE root meaning "to buzz, whisper" (see susurration). Thus the basic sense is perhaps "out of tune," but de Vaan writes, "Since 'deaf' often has two semantic sides, viz. 'who cannot hear' and 'who is not heard,' ab-surdus can be explained as 'which is unheard of' ..." The modern English sense is the Latin figurative one, perhaps "out of harmony with reason or propriety." Related: Absurdly; absurdness.

late 15c., absurdite, "that which is absurd," from Late Latin absurditatem (nominative absurditas) "dissonance, incongruity," noun of state from Latin absurdus "out of tune;" figuratively "incongruous, silly, senseless" (see absurd).

Latin, literally "reduction to the absurd." Absurdum is neuter of absurdus. See reduction + absurd. The tactic is useful and unobjectionable in proofs in geometry.

Middle English dusie, from Old English dysig "foolish, stupid" (obsolete in the original sense except in dialect from 13c.), from Proto-Germanic *dusijaz (source also of Low German düsig "dizzy," Dutch duizelen "to be dizzy," Old High German dusig "foolish," German Tor "fool," Old English dwæs, Dutch dwaas "foolish"), perhaps from PIE *dheu- (1) "dust, vapor, smoke; to rise in a cloud" (and related notions of "defective perception or wits"). Old English used related dyslic to gloss Latin absurdum, which also seems to imply some defect of the senses (see absurd).

The meaning "having a whirling sensation" is from c. 1400; that of "giddy, thoughtless, heedless," is from c. 1500 and seems to merge the two earlier meanings. Used of the "foolish virgins" in early translations of Matthew xxv; used especially of blondes since 1870s. Related: Dizzily.

"in a foolish or absurd manner," 1620s, from silly + -ly (2).

"of the nature of nonsense, absurd, foolish," 1650s, from nonsense + -ical. Related: Nonsensically.

1785, an absurd perversion of (Welsh) rabbit, as if from rare (adj.) + bit (n.). See Welsh.

1610s, from French ineptitude, from Latin ineptitudo, noun of quality from ineptus "unsuitable, absurd" (see inept).

c. 1600, "not fit or suitable, inapt," also "absurd, foolish," from French inepte "incapable" (14c.) or directly from Latin ineptus "unsuitable, improper, impertinent; absurd, awkward, silly, tactless," from in- "not, opposite of" (see in- (1)) + aptus "apt" (see apt). Related: Ineptly; ineptness.

1670s, "absurd thing, object of mockery or contempt;" 1680s, "words or actions meant to invoke ridicule or excite laughter at someone's expense," from French ridicule, noun use of adjective (15c.), or from Latin ridiculum "laughing matter, a joke, a jest," noun use of neuter of ridiculus "laughable, funny, absurd," from ridere "to laugh" (see risible).

"He who brings ridicule to bear against truth, finds in his hand a blade without a hilt." [Walter Savage Landor, "Imaginary Conversations"]