Wordorigins.org

Dizzy sounds like it should be a fairly recent coinage. The double z makes it seem very modern and the word has a slangy air about it. But this couldn’t be further from the truth. Dizzy is a very old word, going back to the Old English dysig or dyseg, meaning foolish or stupid. The word appears in the Vespasian Psalter from c.825:

swe folc dysig
(such dizzy folk)