1590s, "support at the back;" 1640s, "retreat;" verbal noun from back (v.). Physical sense of "anything placed at or attached to the back of something else" is from 1793. Meaning "musical accompaniment" is recorded from 1937.
his vigorous backing of the conservatives got him in trouble with progressives
backgammon
background
backhand
backhanded
backhoe
backing
backlash
backless
backlist
backlog
backorder
