dizzy (adj.)

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").

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.

dizzy (v.)

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.

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Definitions of dizzy from WordNet
dizzy (adj.)
having or causing a whirling sensation; liable to falling;
had a dizzy spell
a dizzy pinnacle
Synonyms: giddy / woozy / vertiginous
dizzy (adj.)
lacking seriousness; given to frivolity;
a dizzy blonde
Synonyms: airheaded / empty-headed / featherbrained / giddy / light-headed / lightheaded / silly
dizzy (v.)
make dizzy or giddy;
a dizzying pace