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.
Flare up! flare up! is all the cry, in every square and street —
No other sound salutes your ear, whoe'er you chance to meet
Where'er you ride, or walk, or sit, or breakfast, dine, or sup,
They welcome you or quiz you with "Flare up, my boy! flare up!"
[Fraser's Magazine, April 1834]
also spazz, by 1959, U.S. teen slang phrase, typically in later use a put-down, apparently a derogatory shortening of spastic (n.). Also used as a verb, by 1972, often with out (adv.). Related: Spazzed; spazzing.
My Daddy is a regular spaz. You don't know what a spaz is? Let me tell you. A spaz is a guy who's completely out of this world—but I mean, completely. [Parade Magazine, March 1, 1959]
[Y]our teen-aged daughter asks what you think of her "shades," which you are canny enough to know are her sunglasses, and you say, "cool," and she says, "oh dad, what a spaz!" [Russell Baker column, April 13, 1965]
1590s, "a 'vocal gesture' expressing the action of puffing anything away" [OED], used as an exclamation of dislike, scorn, or contempt, first attested in Hamlet Act I, Scene III, where Polonius addresses Ophelia with, "Affection! pooh! you speak like a green girl, / Unsifted in such perilous circumstance. / Do you believe his tenders, as you call them?" But the "vocal gesture" is perhaps ancient.