back up (v.)

mid-15c., "to keep something back, hinder," from back (adv.). The meaning "cause to move back" is from 1781. The intransitive sense of "move or go back" is from late 15c. The meaning "furnish with a back or backing" is from 1728, from back (n.). The meaning "to support" (as by a bet) is attested from 1540s. Related: Backed; backing.

Old English up, uppe, from Proto-Germanic *upp- "up" (source also of Old Frisian, Old Saxon up "up, upward," Old Norse upp; Danish, Dutch op; Old High German uf, German auf "up"; Gothic iup "up, upward," uf "on, upon, under;" Old High German oba, German ob "over, above, on, upon"), from PIE root *upo "under," also "up from under," hence also "over."

As a preposition, "to a higher place" from c. 1500; also "along, through" (1510s), "toward" (1590s). Often used elliptically for go up, come up, rise up, etc. Up the river "in jail" first recorded 1891, originally in reference to Sing Sing, which is up the Hudson from New York City. To drive someone up the wall (1951) is from the notion of the behavior of lunatics or caged animals. Insulting retort up yours (scil. ass) is attested by late 19c.

"a standby, a reserve," 1952; see back up (v.). Specific reference to computing is from 1965.