Etymology
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bop (n.)
1948, shortening of bebop or rebop. The musical movement had its own lingo, which was in vogue in U.S. early 1950s. "Life" magazine [Sept. 29, 1952] listed examples of bop talk: crazy "new, wonderful, wildly exciting;" gone (adj.) "the tops--superlative of crazy;" cool (adj.) "tasty, pretty;" goof "to blow a wrong note or make a mistake;" hipster "modern version of hepcat;" dig "to understand, appreciate the subtleties of;" stoned "drunk, captivated, ecstatic, sent out of this world;" flip (v.) "to react enthusiastically."
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madden (v.)

"to drive to distraction, make crazy" (transitive), 1822; earlier in intransitive sense "to be or become mad" (1735), from mad (adj.) + -en (1). Related: Maddened; maddening. The earlier verb was simply mad (14c.), from the adjective.

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loon (n.2)
mid-15c., lowen, louen "rascal, worthless person, boor," of uncertain origin, perhaps from Middle Dutch or Middle Low German; compare Dutch loen "stupid person" (16c.). The modern sense "crazy person" is by influence of loony.
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ding-a-ling (n.)

"one who is crazy," 1940, from earlier adjective (1935), from noun meaning "the sound of little bells" (1894), ultimately imitative of the tinkling sound (by 1848; see ding (v.)). The extended senses are from the notion of hearing bells in the head.

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batty (adj.)
1580s, "pertaining to or resembling a bat or bats," from bat (n.2) + -y (2). Slang sense "nuts, crazy" is attested from 1903, from the colloquial expression (to have) bats in (one's) belfry "not be right in the head" (1899).
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potty (adj.)

"crazy, silly," 1916, slang, of unknown origin, perhaps connected to potter (v.), or to pot (n.1) in its association with alcoholic drinking. Earlier slang senses were "easy to manage" (1899) and "feeble, petty" (1860).

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flaky (adj.)

1570s, "consisting of flakes," from flake + -y (2). Meaning "eccentric, crazy" first recorded 1959, said to be American English baseball slang, but probably from earlier druggie slang flake "cocaine" (1920s). Flake (n.) "eccentric person" is a 1968 back-formation from it. Related: Flakiness.

The term 'flake' needs explanation. It's an insider's word, used throughout baseball, usually as an adjective; someone is considered 'flaky.' It does not mean anything so crude as 'crazy,' but it's well beyond 'screwball' and far off to the side of 'eccentric.' [New York Times, April 26, 1964]
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Catch-22 (n.)

from the title of Joseph Heller's 1961 novel. In widespread use only after release of the movie based on the book in 1970. The catch (n.) is that a bomber pilot is insane if he flies combat missions without asking to be relieved from duty and thus is eligible to be relieved from duty. But asking to be relieved from duty indicates sanity and thus he must keep flying missions.

There was only one catch and that was Catch-22, which specified that a concern for one's safety in the face of dangers that were real and immediate was the process of a rational mind. Orr was crazy and could be grounded. All he had to do was ask; and as soon as he did, he would no longer be crazy and would have to fly more missions. Orr would be crazy to fly more missions and sane if he didn't, but if he was sane he had to fly them. If he flew them he was crazy and didn't have to; but if he didn't want to he was sane and had to. Yossarian was moved very deeply by the absolute simplicity of this clause of Catch-22 and let out a respectful whistle.

"That's some catch, that Catch-22," he observed.

"It's the best there is," Doc Daneeka agreed.
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nerd (n.)
1951, U.S. student slang, probably an alteration of 1940s slang nert "stupid or crazy person," itself an alteration of nut. The word turns up in a Dr. Seuss book from 1950 ("If I Ran the Zoo"), which may have contributed to its rise.
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nutter (n.)

late 15c., "one who gathers nuts," from nut + -er (1). Meaning "crazy person" is British slang, by 1958, from nut + -er (3). Nuttery "mental hospital" is attested in slang from 1931; earlier it meant "place for storing nuts" (1881).

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