late Old English hyttan, hittan "come upon, meet with, fall in with, 'hit' upon," from a Scandinavian source such as Old Norse hitta "to light upon, meet with," also "to hit, strike;" Swedish hitta "to find," Danish and Norwegian hitte "to hit, find," from Proto-Germanic *hitjan, which is of uncertain origin. Meaning shifted in late Old English period to "strike, come into forcible contact" via the notion of "to reach with a blow or missile," and the word displaced Old English slean (modern slay) in this sense. Original sense survives in phrases such as hit it off (1780, earlier in same sense hit it, 1630s) and is revived in slang hit on (1970s).
To hit the bottle "drink alcohol" is from 1933 (hit the booze in the same sense is from 1889, and hit the pipe "smoke opium" is also late 19c.). To figuratively hit the nail on the head (1570s) is from archery. To hit the hay "go to bed" is from 1912. Hit the road "leave" is from 1873; hit the bricks is from 1909, originally trade union jargon meaning "go out on strike." To hit (someone) up "request something" is from 1917. To not know what hit (one) is from 1923. Related: Hitting.
"provide a roof for, cover with a roof," early 15c., rofen, from roof (n.). Related: Roofed; roofing.
"outer upper covering of a house or other building," Middle English rof, from Old English hrof "roof," also "ceiling," hence figuratively "highest point, top, summit" also "heaven, the sky;" from Proto-Germanic *khrofam (source also of Old Frisian rhoof "roof," Middle Dutch roof, rouf "cover, roof," Dutch roef "deckhouse, cabin, coffin-lid," Middle High German rof "penthouse," Old Norse hrof "boat shed").
No apparent connections outside Germanic. "English alone has retained the word in a general sense, for which the other languages use forms corresponding to OE. þæc thatch" [OED]. Meaning "top of a carriage, etc." is by 1706. The meaning "upper part of the mouth, the hard palate" was in late Old English (hrof ðæs muðes). To raise the roof "create an uproar" is attested from 1860, originally in U.S. Southern dialect.
late 15c., "a rebuke;" 1590s, "a blow, stroke," from hit (v.). Meaning "successful play, song, person," etc., 1811, is from the verbal sense of "to hit the mark, succeed" (c. 1400). Underworld slang meaning "a killing" is from 1970, from the criminal slang verb meaning "to kill by plan" (1955). Meaning "dose of narcotic" is 1951, from phrases such as hit the bottle.
Old English þæc "roof, thatch, cover of a building," from Proto-Germanic *thakam (source also of Old Norse þak, Old Frisian thek, Swedish tak, Danish tag, Middle Dutch, Dutch dak "roof," Old High German dah "covering, cover," German Dach "roof"), from PIE root *(s)teg- "to cover."
"to form with a vault or arched roof," late 14c., from Old French vaulter, volter, from voute "arch, vaulted roof" (see vault (n.1)). Related: Vaulted; vaulting.