butt (n.1) Look up butt at Dictionary.com
"thick end," O.E. buttuc "end, small piece of land," akin to O.N. butr "short." In sense of "human posterior" it is recorded from 1450. Meaning "remainder of a smoked cigarette" first recorded 1847.
butt (n.2) Look up butt at Dictionary.com
"barrel," 1385, from Anglo-Norm. but and O.Fr. bot/bout, from L.L. buttis "cask," probably from Gk. (see bottle). Usually a cask holding 108 to 140 gallons, or roughly two hogsheads, but the measure varied greatly.
butt (n.3) Look up butt at Dictionary.com
"target of a joke," 1616, originally "target for shooting practice" (1345), from O.Fr. but "aim, goal, end," perhaps from butte "mound, knoll," from Frank. *but (cf. O.N. butr "long of wood"), which would connect it with butt (n.1).
butt (v.) Look up butt at Dictionary.com
"hit with the head," c.1200, from Anglo-Norm. buter, from O.Fr. boter "to thrust against," from V.L. *bottare "thrust," or from Frankish (cf. O.N. bauta, Low Ger. boten "to strike, beat"), from P.Gmc. *butan, from PIE base *bhau- "to strike" (see batter (v.)). To butt in "rudely intrude" is Amer.Eng., 1900.