plum n.

"fruit of the genus Prunus," Middle English ploume, from Old English plume "plum, plum tree," from an early Germanic borrowing (Middle Dutch prume, Dutch pruim, Old High German pfluma, pfruma, German Pflaume) from Vulgar Latin *pruna, from Latin prunum "plum," from Greek prounon, a later form of proumnon, a word of unknown origin, which is probably, like the tree itself, of Anatolian origin. Also see prune (n.). The change of pr- to pl- is peculiar to some Germanic languages. The vowel shortened in early modern English. Meaning "something desirable, the best or choicest part" is first recorded 1780, probably in reference to the sugar-rich bits of a plum pudding, etc.