"covering for the foot and lower leg," early 14c., from Old French bote "boot" (12c.), with corresponding words in Provençal, Spanish, and Medieval Latin, all of unknown origin, perhaps from a Germanic source. Originally of riding boots only.
From c. 1600 as "fixed external step of a coach." This later was extended to "low outside compartment used for stowing luggage" (1781) and hence the transferred use, of motor vehicles, in Britain, where American English has trunk (n.1).
Boot-black "person who shines boots and shoes" is from 1817; boot-jack "implement to hold a boot by the heel while the foot is drawn from it" is from 1793. Boot Hill, U.S. frontier slang for "cemetery" (1893, in a Texas panhandle context) probably is an allusion to dying with one's boots on. An old Dorsetshire word for "half-boots" was skilty-boots [Halliwell, Wright].
"profit, use," Old English bot "help, relief, advantage; atonement," literally "a making better," from Proto-Germanic *boto (see better (adj.)). Compare Old Frisian bote "fine, penalty, penance, compensation," German Buße "penance, atonement," Gothic botha "advantage, usefulness, profit." Now mostly in phrase to boot (Old English to bote), indicating something thrown in by one of the parties to a bargain as an additional consideration.
"to kick, drive by kicking," 1877, American English, from boot (n.1). Earlier "to beat with a boot" (a military punishment), 1802. Generalized sense of "eject, kick (out)" is from 1880. To give (someone) the boot "dismiss, kick out" is from 1888. Related: Booted; booting.
1975, transitive, "start up (a computer) by causing an operating system to load in the memory," 1975, from bootstrap (v.), a 1958 derived verb from bootstrap (n.) in the computer sense "fixed sequence of instructions to load the operating system of a computer" (1953). This is from the notion of the first-loaded program pulling itself (and the rest) up by the bootstrap, an old expression for "better oneself by rigorous, unaided effort." Intransitive, of a computer operating system, from 1983. Related: Booted; booting.