Etymology
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it (pron.)

Old English hit, neuter nominative and accusative of third person singular pronoun, from Proto-Germanic demonstrative base *khi- (source also of Old Frisian hit, Dutch het, Gothic hita "it"), from PIE *ko- "this" (see he). Used in place of any neuter noun, hence, as gender faded in Middle English, it took on the meaning "thing or animal spoken about before."

The h- was lost due to being in an unemphasized position, as in modern speech the h- in "give it to him," "ask her," is heard only "in the careful speech of the partially educated" [Weekley]. It "the sex act" is from 1610s; meaning "sex appeal (especially in a woman)" first attested 1904 in works of Rudyard Kipling, popularized 1927 as title of a book by Elinor Glyn, and by application of It Girl to silent-film star Clara Bow (1905-1965). In children's games, the meaning "the one who must tag or catch the others" is attested from 1842.

From Old English as nominative of an impersonal verb or statement when the thing for which it stands is implied (it rains, it pleases me). After an intransitive verb, used transitively for the action denoted, from 1540s (originally in fight it out). That's it "there is no more" is from 1966; this is it "the anticipated or dreaded moment has arrived" is from 1942.

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snuff (n.)
"powdered tobacco to be inhaled," 1680s, from Dutch or Flemish snuf, shortened form of snuftabak "snuff tobacco," from snuffen "to sniff, snuff" (see snuff (v.2)). The practice became fashionable in England c. 1680. Slang phrase up to snuff "knowing, sharp, wide-awake, not likely to be deceived" is from 1811; the exact sense is obscure unless it refers to the "elevating" properties of snuff.
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snuff (v.1)
"to cut or pinch off the burned part of a candle wick," mid-15c., from noun snoffe "burned part of a candle wick" (late 14c.), of unknown origin, perhaps related to snuff (v.2). The meaning "to die" is from 1865; that of "to kill" is from 1932; snuff-film, originally an urban legend, is from 1975.
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snuff (v.2)
"draw in through the nose," 1520s, from Dutch or Flemish snuffen "to sniff, snuff," related to Dutch snuiven "to sniff," from Proto-Germanic *snuf- (source also of Middle High German snupfe, German Schnupfen "head-cold"), imitative of the sound of drawing air through the nose (see snout). Related: Snuffed; snuffing.
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know-it-all (n.)
"one deemed (over)full of information or correct answers," 1895, from verbal phrase; see know (v.). Earlier in the same sense was know-all (1862); and Mr. Know-All was a minor character in Bunyan's "The Holy War" (1682).
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go-it-alone (adj.)
attested by 1953 (in reference to U.S. foreign policy proposals), from an American English verbal phrase attested by 1842 and meaning "do anything without assistance." Go it as colloquial for "to act" (especially in a determined or vigorous way) is from 1825; hence also American English go it blind (1842) in reference to something done without regard for consequences.
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do-it-yourself (adj.)

as a modifier, attested by 1941. The expression is much older (1610s). Related: Do-it-yourselfer.

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snuffer (n.)
also snuffter, "instrument for cropping the snuff of a candle, with a closed box to contain the burnt smell and smoke," mid-15c., agent noun from snuff (v.1).
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