Etymology
Advertisement
labor (v.)
late 14c., "perform manual or physical work; work hard; keep busy; take pains, strive, endeavor" (also "copulate"), from Old French laborer "to work, toil; struggle, have difficulty; be busy; plow land," from Latin laborare "to work, endeavor, take pains, exert oneself; produce by toil; suffer, be afflicted; be in distress or difficulty," from labor "toil, work, exertion" (see labor (n.)).

The verb in modern French, Spanish, and Portuguese means "to plow;" the wider sense being taken by the equivalent of English travail. Sense of "endure pain, suffer" is early 15c., especially in phrase labor of child (mid-15c.). Meaning "be burdened" (with trouble, affliction, etc., usually with under) is from late 15c. The transitive senses have tended to go with belabor. Related: Labored; laboring.
Related entries & more 
Advertisement
screw (v.)

1590s, transitive, "twist (something) like a screw, turn or cause to turn by the sort of pressure that advances a screw," " from screw (n.). From 1610s as "to attach or tighten with a screw."

Meaning "defraud, cheat" is from 1900; earlier it was "press hard upon, oppress" (1620s). Related: Screwed; screwing.

The slang meaning "to copulate" dates from at least 1725, originally usually of the action of the male, on the notion of driving a screw into something; screw is recorded by 1949 in exclamations as a euphemism. To screw up "to blunder" is recorded from 1942, earlier it was "to raise (rent or payment) exorbitantly" (1630s). The U.S. slang noun screw-up "a blunder, a mess" is by 1960, from the verbal phrase. Expression to have (one's) head screwed on the right (or wrong) way is from 1821. Screw your courage to the sticking place is Lady Macbeth.

Related entries & more 
cover (v.)
Origin and meaning of cover

mid-12c., "protect or defend from harm," from Old French covrir "to cover, protect, conceal, dissemble" (12c., Modern French couvrir), from Late Latin coperire, from Latin cooperire "to cover over, overwhelm, bury," from assimilated form of com-, here perhaps an intensive prefix (see com-), + operire "to close, cover," from PIE compound *op-wer-yo-, from *op- "over" (see epi-) + root *wer- (4) "to cover."

Sense of "to hide or screen" is from c. 1300, that of "to put something over (something else)" is from early 14c. Sense of "spread (something) over the entire extent of a surface" is from late 14c. Military sense of "aim at" is from 1680s; newspaper sense first recorded 1893; use in U.S. football dates from 1907. Betting sense "place a coin of equal value on another" is by 1857. Of a horse or other large male animal, as a euphemism for "copulate with" it dates from 1530s.

Meaning "to include, embrace, comprehend" is by 1868. Meaning "to pass or travel over, move through" is from 1818. Sense of "be equal to, be of the same extent or amount, compensate for" is by 1828. Sense of "take charge of in place of an absent colleague" is attested by 1970.

Related entries & more 

Page 3