Backing
来自Big Physics
Old English bæc, of Germanic origin; related to Middle Dutch and Old Norse bak . The adverb use dates from late Middle English and is a shortening of aback.
wiktionary
back + -ing
etymonline
backing (n.)
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.
