Etymology
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knock (v.)
Old English cnocian (West Saxon cnucian), "to pound, beat; knock (on a door)," likely of imitative origin. Figurative meaning "deprecate, put down" is from 1892. Related: Knocked; knocking. Of engines from 1869. To knock back (a drink) "swallow quickly or at a gulp" is from 1931. Many phrases are in reference to the auctioneer's hammer, for example knock down (v.) "dispose of (something) at auction" (1760).
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knock (n.)
mid-14c., from knock (v.). As an engine noise, from 1899.
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knock-down (adj.)
also knockdown, 1680s, from the verbal phrase knock down, attested from mid-15c. in the sense "fell to the ground;" see knock (v.) + down (adv.). As a noun from 1809. Phrase knock-down, drag-out is from 1827.
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knock up (v.)

1660s, "arouse by knocking at the door," from knock (v.) + up (adv.). However it is little used in this sense in American English, where the phrase means "get a woman pregnant" (1813), possibly ultimately from knock in a sense "to copulate with" (1590s; compare slang knocking-shop "brothel," 1860).

Knocked up in the United States, amongst females, the phrase is equivalent to being enciente, so that Englishmen often unconsciously commit themselves when amongst our Yankee cousins. [John Camden Hotten, "The Slang Dictionary," London, 1860]
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knocker (n.)
late 14c., agent noun from knock (v.). Sense of "door banger" is by 1590s. Knockers "a woman's breasts" is slang attested from 1941.
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knockabout (adj.)
also knock-about, "suitable for anything," 1876, from verbal phrase knock about (intrans.) "wander here and there" (1833; knock around in the same sense is from 1848); see knock (v.) + around (adv.).
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knockout (n.)
also knock-out, in fighting, 1887, from verbal phrase knock out "to stun by a blow for a 10-count" in boxing, short for to knock out of time; see knock (v.) + out (adv.). Slang meaning "excellent thing or person" is from 1892; specifically "beautiful woman" by 1953. As an adjective from 1896 in the tournament competition sense, 1898 in fighting. To knock oneself out "make a great effort" is from 1936.
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knockoff (n.)
also knock-off, "cheap imitation," 1966, from the verbal phrase knock off "do hastily" (1817), in reference to the casual way the things are made. The verbal phrase knock off is attested from 1640s as "desist, stop" (work, study, etc.), hence knockoff (n.) "act of leaving work" (1899) and, probably, the command knock it off "stop it" (1880), which was perhaps reinforced by the auctioneer's use of the term for "dispose of quickly." To knock (someone) off in the underworld slang sense of "kill, murder" is from 1919. See knock (v.) + off (adv.).
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gnarled (adj.)

c. 1600, probably a variant of knurled, from Middle English knar "knob, knot in wood, protruding mass on a tree" (late 14c.), earlier "a crag, rugged rock or stone" (early 13c.), from a general group of Germanic words that includes English knob, knock, knuckle, knoll, knurl. Gnarl (v.) "make knotty," gnarl (n.) "a knotty growth on wood," and gnarly (adj.) all seem to owe their existence in modern English to Shakespeare's use of gnarled in 1603:

[T]hy sharpe and sulpherous bolt Splits the vn-wedgable and gnarled Oke. ["Measure for Measure," II.ii.116]

"(Gnarled) occurs in one passage of Shakes. (for which the sole authority is the folio of 1623), whence it came into general use in the nineteenth century" [OED].

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