1942, apparently first attested in the Walt Disney movie "Bambi" (there also was a song by that name but it was not in the studio release of the film), a past-participle adjective formed from twitter in the "tremulous excitement" noun sense (1670s) + pate (n.2) "head" (compare flutterpated, 1894).
Thumper: Why are they acting that way?
Friend Owl: Why, don't you know? They're twitterpated.
Flower, Bambi, Thumper: Twitterpated?
Friend Owl: Yes. Nearly everybody gets twitterpated in the springtime. For example: You're walking along, minding your own business. You're looking neither to the left, nor to the right, when all of a sudden you run smack into a pretty face. Woo-woo! You begin to get weak in the knees. Your head's in a whirl. And then you feel light as a feather, and before you know it, you're walking on air. And then you know what? You're knocked for a loop, and you completely lose your head!
Thumper: Gosh, that's awful.