buck (n.1) Look up buck at Dictionary.com
"male deer," c.1300, earlier "male goat;" from O.E. bucca "male goat," from P.Gmc. *bukkon (cf. M.Du. boc, O.H.G. boc, O.N. bokkr), perhaps from a PIE base *bhugo (cf. Avestan buza "buck, goat," Arm. buc "lamb"), but some speculate that it is from a lost pre-Gmc. language. Barnhart says O.E. buc "male deer" is a "ghost word or scribal error." Meaning "dollar" is 1856, Amer.Eng., perhaps an abbreviation of buckskin, a unit of trade among Indians and Europeans in frontier days, attested in this sense from 1748. Pass the buck is first recorded in the lit. sense 1865, Amer.Eng.:
"The 'buck' is any inanimate object, usually knife or pencil, which is thrown into a jack pot and temporarily taken by the winner of the pot. Whenever the deal reaches the holder of the 'buck', a new jack pot must be made." [J.W. Keller, "Draw Poker," 1887]
The fig. sense of "shift responsibility" is first recorded 1912. Buck private is recorded by 1870s, of uncertain signification.
buck (v.) Look up buck at Dictionary.com
1848, apparently with a sense of "jump like a buck," from buck (n.1). Buck up "cheer up" is from 1844.
buck (n.2) Look up buck at Dictionary.com
"sawhorse," 1817, Amer.Eng., apparently from Du. bok "trestle."