Etymology
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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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drag (v.)

late 14c., draggen, "to draw a grapnel along the bottom of a river, lake, etc., in search of something;" late 15c., "to draw away by force, pull haul," from Old Norse draga, or a dialectal variant of Old English dragan "to draw," both from Proto-Germanic *draganan "to draw, pull," perhaps from a PIE *dhregh- "to draw, drag on the ground" (source also of Sanskrit dhrajati "pulls, slides in," Russian drogi "wagon," doroga "way;"  connection to Latin trahere "to draw" is possible but problematic).

Meaning "draw (feet, tails, etc.) along slowly" is from 1580s; intransitive sense of "move heavily or slowly, hang with its weight while moving or being moved" is by 1660s. Meaning "to take a puff" (of a cigarette, etc.) is from 1914. Related: Dragged; dragging. Drag-out "violent fight" is from c. 1859. To drag (one's) feet (1946 in the figurative sense "delay deliberately") supposedly is from logging, from a lazy way to use a two-man saw.

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drag (n.)

c. 1300, dragge, "dragnet," perhaps from a Scandinavian source (compare Old Norse dragga "a load," Swedish dragg "grapnel") or from Old English dræge "dragnet," related to dragan "to draw" (see drag (v.)).

From 1708 as "anything attached to a moving body that retards its progress." As the name of a device for retarding or stopping the rotation of wheels, 1795. Sense of "annoying, boring person or thing" is 1813, perhaps from the mechanical senses or the notion of something that must be dragged as an impediment.

Sense of "women's clothing worn by a man" is by 1870, perhaps originally theater slang, from the sensation of long skirts trailing on the floor (another guess is Yiddish trogn "to wear," from German tragen); drag queen "male transvestite or cross-dresser" is from 1941.

Drag racing (1947), is said to be from thieves' slang drag "automobile" (1935), perhaps ultimately from slang sense of "wagon, buggy" (1755), because a horse would drag it. By 1851 this was transferred to "street," as in the phrase main drag (which some propose as the source of the racing sense).

In addition to the time trials there are a number of "drag races" between two or more cars. They are run, not for record, but to satisfy the desire of most Americans to see who can get from here to there in the fastest time. [Popular Mechanics, January 1947]
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knock (n.)

mid-14c., from knock (v.). As an engine noise, from 1899.

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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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out-and-out 

c. 1300 as an adverbial phrase, "completely, thoroughly, to the utmost degree," from out (adv.). Adjective usage is attested by 1813.

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down (adj.)

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.

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down (adv.)

"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.

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down (n.3)

1710, "a downward movement," from down (adv.). Football sense of "an attempt to advance the ball" is by 1882.

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out- 

in Old English a common prefix with nouns, adjectives, adverbs, and verbs, "out, outward, outer; forth, away," from out (adv.). The use was even more common in Middle English, and also with the senses "outer, outside, on the outside, from without, external, externally; apart; greatly, extremely; completely, thoroughly, to completion." Other senses of out that extended into the use as a prefix include "beyond the surface or limits; to the utmost degree; to an explicit resolution."

In composition out has either its ordinary adverbial sense, as in outcast, outcome, outlook, etc., or a prepositional force, as in outdoors, or forms transitive verbs denoting a going beyond or surpassing of the object of the verb, in doing the act expressed by the word to which it is prefixed, as in outrun, outshine, outvenom, etc. In the last use especially out may be used with almost any noun or verb. [Century Dictionary]
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