1540s, alteration of pommel in the verbal sense of "to beat repeatedly" with a pommel or with something thick and bulky. In early use pumble, poumle; current spelling from c. 1600. Related: Pummeled; pummeling.

1640s, alteration of pompone, pumpion "melon, pumpkin" (1540s), from Middle French pompon, from Latin peponem (nominative pepo) "melon," from Greek pepon "melon," probably originally "cooked (by the sun)," hence "ripe;" from peptein "to cook" (from PIE root *pekw- "to cook, ripen"). Pumpkin-pie is recorded from 1650s. Pumpkin-head, American English colloquial for "person with hair cut short all around" is recorded from 1781. Vulgar American English alternative spelling punkin attested by 1806.

America's a dandy place:

The people are all brothers:

And when one's got a punkin pye,

He shares it with the others.

[from "A Song for the Fourth of July, 1806," in The Port Folio, Philadelphia, Aug. 30, 1806]

1660s (first attested in Dryden), of uncertain origin, perhaps from pundigron, which is perhaps a humorous alteration of Italian puntiglio "equivocation, trivial objection," diminutive of Latin punctum "point." This is pure speculation. The verb also is attested from 1660s. Related: Punned; punning.

Pun was prob. one of the clipped words, such as cit, mob, nob, snob, which came into fashionable slang at or after the Restoration. [OED]