"excavating equipment consisting of a digging bucket on the end of an articulated arm, typically mounted on the back of a tractor," by 1928, from back (n. or adj.) + hoe (n.).
1900, "material taken from an excavation used to fill a depression," 1900, from back fill (v.), which is attested by 1880; see back (adv.) + fill (v.).
also back-track, "retrace one's steps," figuratively by 1896, from literal sense, with reference to hunted foxes; see back (adv.) + track (v.). Related: Backtracked; backtracking.