giddy (adj.)
Old English gidig, variant of gydig "insane, mad, stupid," perhaps literally "possessed (by a spirit)," if it is from Proto-Germanic *gud-iga- "possessed by a god," from *gudam "god" (see god (n.)) + *-ig "possessed." Meaning "having a confused, swimming sensation" is from 1560s (compare sense evolution of dizzy). Meaning "elated" is from 1540s. Related: Giddily; giddiness.