Merriam-Webster's Collegiate® Dictionary, 11th Edition
GIDDY
I. adjective (giddier; -est)
Etymology: Middle English gidy mad, foolish, from Old English gydig possessed, mad; akin to Old English god god
Date: 14th century
1. dizzy , causing dizziness , whirling rapidly,
2. lightheartedly silly ; frivolous , joyfully elated ; euphoric, giddily adverb giddiness noun
II. verb (giddied; giddying)
Date: 1602
transitive verb to make giddy, intransitive verb to become giddy