"a whispering, a murmur," c. 1400, susurracioun, from Latin susurrationem (nominative susurratio), noun of action from past-participle stem of susurrare "to hum, murmur," from susurrus "a murmur, whisper." This is held to be a reduplication of a PIE imitative *swer- "to buzz, whisper" (source also of Sanskrit svarati "sounds, resounds," Greek syrinx "flute," Latin surdus "dull, mute," Old Church Slavonic svirati "to whistle," Lithuanian surma "pipe, shawm," German schwirren "to buzz," Old English swearm "a swarm").

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).

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.

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