c. 1300, "to fall (into water) or strike with a full impact," a common Low German word, from or related to Middle Dutch and Dutch plompen, East Frisian plumpen, Middle Low German plumpen, probably more or less imitative of something hard striking something soft. Perhaps influenced by or merged with Middle English plumben "immerse (in liquid)," late 14c., from plumb (n.) in the "weight" sense. Hence plump (n.) "a firm blow," in pugilism usually one to the belly.
To plump; to strike, or shoot. I'll give you a plump in the bread basket, or the victualling office; I'll give you a blow in the stomach. [Grose, "Dictionary of the Vulgar Tongue," London, 1785]
Or, even if any of them should suspect me, I know how to bring myself off. It is but pretending to be affronted, stripping directly, challenging him to fight, and before he can be on his guard, hitting him a plump in the bread-basket, that shall make him throw up his accounts; and I'll engage he will have but very little stomach to accuse me after. ["The Reverie: or A Flight to the Paradise of Fools," London, 1763]
As an adverb, "at once," as in a sudden fall, from 1590s.
late 15c., "blunt, dull" (in manners), from Dutch plomp "blunt, thick, massive, stumpy," probably related to plompen "fall or drop heavily" (see plump (v.)). Meaning "full and well-rounded," of a person, "fleshy, chubby," is from 1540s in English. Danish and Swedish plump "rude, coarse, clumsy" are from the Low German word and represent a different sense development. Middle English plump (n.) "a compact group of people, a crowd" (c. 1400) perhaps is from Middle Dutch as well.
1530s, "to become plump," from plump (adj.). Transitive meaning "to plump (something) up, to cause to swell" is from 1530s. Related: Plumped; plumping.
1560s, "directed downward," from down (adv.). Sense of "depressed mentally" is attested from c. 1600. Slang sense of "aware, wide awake" is attested from 1812. Computer crash sense is from 1965. Down-and-out "completely without resources" is from 1889, American English, from situation of a beaten prizefighter.
"in a descending direction, from a higher to a lower place, degree, or condition," late Old English shortened form of Old English ofdune "downwards," originally of dune "off from (the) hill," from dune "from the hill," dative of dun "hill" (see down (n.2)). The "hill" word is general in Germanic, but this sense development is peculiar to English. As a preposition, "in a descending direction upon or along," from late 14c.
To be down on "express disapproval of" is by 1851. Down home is from 1828 as "in one's home region," as an adjective phrase meaning "unpretentious" by 1931, American English. Down the hatch as a toast is from 1931. Down to the wire is 1901, from horse-racing.
Down Under "Australia and New Zealand" attested from 1886; Down East "Maine" is from 1825; Down South "in the Southern states of the U.S." is attested by 1834. Down the road "in the future" is by 1964, U.S. colloquial. Down-to-earth "everyday, ordinary, realistic" is by 1932.
1710, "a downward movement," from down (adv.). Football sense of "an attempt to advance the ball" is by 1882.
"first feathers of a baby bird; soft covering of fowls under the feathers, the under-plumage of birds," used for stuffing pillows and feather-beds, mid-14c., from Old Norse dunn, which is of uncertain origin. Extended in Modern English to the soft hair of the human face and fine soft pubescence upon plants and some fruit.
"a hill of moderate elevation and more or less rounded outline," Old English dun "height, hill, moor," from Proto-Germanic *dunaz- (source also of Middle Dutch dunen "sandy hill," Dutch duin), "probably a pre-insular loan-word from Celtic" [Cambridge Dictionary of English Place-Names], in other words, borrowed at a very early period, before the Anglo-Saxon migration, perhaps from PIE root *dheue- "to close, finish, come full circle."
The more general meaning "elevated rolling grassland; high, rolling region not covered by forest" is from c. 1400. Specifically of certain natural pastureland districts of south and southeast England (the Downs) by mid-15c.
The non-English Germanic words tend to mean "dune, sand bank" (see dune), while the Celtic cognates tend to mean "hill, citadel" (compare Old Irish dun "hill, hill fort;" Welsh din "fortress, hill fort;" and second element in place names London, Verdun, etc.). German Düne, French dune, Italian, Spanish duna are said to be loan-words from Dutch.
1560s, "cause to go down," from down (adv.). Meaning "swallow hastily" is by 1860; football sense of "bring down (an opposing player) by tackling" is attested by 1887. Figurative sense of "defeat, get the better of" is by 1898. Related: Downed; downing.