Meaning

adjective having or causing a whirling sensation; liable to falling

adjective lacking seriousness; given to frivolity

originThe adjective is derived from Middle English gidi, gedy, gydy (“demonically controlled or possessed; crazy, insane; foolish, idiotic, ridiculous, unwise; unsure; (rare) dizzy, shaky; (rare) of an animal: crazed, out of control; a fool”) [and other forms], from Old English gidiġ, gydiġ (“possessed by a demon or spirit, insane, mad”), from Proto-West Germanic *gudīg (“ghostly, spirited”, literally…

Etymology from Wiktionary, CC BY-SA 3.0