Giddy

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Old English gidig ‘insane’, literally ‘possessed by a god’, from the base of God. Current senses date from late Middle English.

wiktionary

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From Middle English guidie, guydie, gydi(“possessed by a demon; crazy, insane; foolish; dizzy”), from Old English gidiġ, gydiġ(“possessed by a spirit or demon, mad, insane”), from Proto-Germanic *gudīgaz(“ghostly, spirited”, literally “possessed by a god or spirit”), equivalent to god +‎ -y.

etymonline

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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.