Etymology
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chaps (n.2)

"jaws, cheeks," from chap (n.), 1550s, which is of unknown origin. Hence, chap-fallen "with the lower jaw hanging down" (1590s), hence, figuratively, "dejected, disspirited" (c. 1600).

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chaps (n.1)

1844, American English, short for chaparejos, from Mexican Spanish chaparreras, leather overalls worn to protect riders' legs from the chaparro (see chaparral).

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chops (n.)
"jaws, sides of the face," c. 1500, perhaps a variant of chaps (n.2) in the same sense, which is of unknown origin.
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punch (n.3)

"a quick blow, dig, or thrust with the fist," by 1570s, probably from punch (v.). In early use it also could refer to blows with the foot or jabs with a staff or club. Originally especially of blows that sink in to some degree ("... whom he unmercifully bruises and batters from head to foot: here a slap in the chaps, there a black eye, now a punch in the stomach, and then a kick on the breech," Monthly Review, 1763).

The figurative sense of "forceful, vigorous quality" is recorded from 1911. Punch line (also punch-line) is from 1915, originally in popular-song writing. To beat (someone) to the punch in the figurative sense is from 1915, a metaphor from boxing (attested by 1913); punch-drunk "dazed from continued punching, having taken so many punches one can no longer feel it" is from 1915 (alternative form slug-nutty is from 1933).

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