dizzy adj.

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.

Middle English dusien, from Old English dysigan "do unwise or foolish things," from the source of dizzy (adj.). Sense of "to make to have a whirling sensation" is from c. 1500. Related: Dizzied; dizzying.