Etymology
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damp (n.)

early 14c., "noxious vapor in a coal mine, fire-damp, stifling poisonous gas," perhaps in Old English but there is no record of it. If not, probably from Middle Low German damp; ultimately in either case from Proto-Germanic *dampaz (source also of Old High German damph, German Dampf "vapor;" Old Norse dampi "dust"). Sense of "moist air, moisture, humidity" is not easily distinguished from the older sense but is certainly attested by 1706.

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damp (v.)

late 14c., "to suffocate" (with or as with damp, foul air in a mine), from damp (n.). Figurative meaning "to check or retard the force or action of (the spirits, etc.)" is attested by 1540s. Meaning "to moisten" is recorded from 1670s. Century Dictionary (1897) states that "Dampen is now more common in the literal sense, and is sometimes used in the derived senses." Related: Damped; damping.

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damp (adj.)

1580s, "dazed," from damp (n.). Meaning "slightly wet" is from 1706. Related: Damply; dampness.

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course (v.)
Origin and meaning of course

mid-15c., "to pursue, hound" (obsolete); 1530s, "to run, pass over," from course (n.). Related: Coursed; coursing.

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course (n.)
Origin and meaning of course

c. 1300, "onward movement, motion forward, a running in a prescribed direction or over a prescribed distance; path or distance prescribed for a race, a race-course" from Old French cors "course; run, running; flow of a river" (12c.), from Latin cursus "a running; a journey; direction, track navigated by a ship; flow of a stream;" from curs- past participle stem of currere "to run" (from PIE root *kers- "to run").

Also from c. 1300 as "order, sequence;" meanings "habitual or ordinary procedure" (as in course of nature) and "way of life, personal behavior or conduct" are from early 14c.

Most of the extended senses developed 14c. from notion of "line in which something moves" (as in hold one's course) or "stage through which something must pass in its progress." Thus, via the meaning "series or succession in a specified or systematized order" (mid-14c.) comes the senses of "succession of prescribed acts intended to bring about a particular result" (c. 1600, as in course of treatment) and the academic meaning "planned series of study" (c. 1600; in French from 14c.), also "that part of a meal which is served at once and separately" (late 14c.).

Meaning "the flow of a stream of water" is from mid-14c.; that of "channel in which water flows" is from 1660s. Courses was used for the flow of bodily fluids and 'humors' from late 14c.; specifically of menstrual flux from 1560s.

Adverbial phrase of course "by consequence, in regular or natural order" is attested from 1540s, literally "of the ordinary course;" earlier in the same sense was bi cours (c. 1300). Matter of course "something to be expected" is by 1739.

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proof (v.)

1834, "to test," from proof (n.). From 1950 as short for proof-read (v.). Related: Proofed; proofing.

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proof (n.)

c. 1200, preove "evidence and argumentation to establish the fact of (something) beyond reasonable doubt," from Anglo-French prove, preove, Old French proeve, prueve "proof, test, experience" (13c., Modern French preuve), from Late Latin proba "a proof," a back-formation from Latin probare "to prove" (see prove). "The devocalization of v to f ensued upon the loss of final e; cf. the relation of v and f in believe, belief, relieve, relief, behove, behoof, etc." [OED].

The meaning "act of proving" is early 14c. The meaning "act of testing or making trial of anything" is from late 14c., from influence of prove. Meaning "standard of strength of distilled liquor" is from 1705, on the notion of "having been tested as to degree of strength." The use in photography is from 1855. The typographical sense of "trial impression to test type" is from c. 1600. The numismatic sense of "coin struck to test a die" is from 1762; now mostly in reference to coins struck from highly polished dies, mainly for collectors.

The adjectival sense "impenetrable, able to resist" (as in proof against) is recorded from 1590s, from the noun in expressions such as proof of (mid-15c.), hence extended senses involving "of tested power against" in compounds such as fireproof (1630s), rust-proof (1690s), waterproof (1725), fool-proof (1902), etc. Shakespeare has shame-proof. Expression the proof is in the pudding (1915) is a curious perversion of earlier proof of the pudding shall be in the eating (1708), with proof in the sense "quality of proving good or turning out well" (17c.).

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fire-damp (n.)
"marsh gas," 1670s, from fire (n.) + damp (n.) "noxious vapor." Largely methane, it can spontaneously ignite when mixed with atmospheric air.
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bullet-proof (adj.)
also bulletproof, 1816, from bullet (n.) + proof (n.).
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