holdback

n. 1. Check; hindrance; restraint; obstacle. [ 1913 Webster ]

The only holdback is the affection . . . that we bear to our wealth. Hammond. [ 1913 Webster ]

2. The projection or loop on the thill of a vehicle. to which a strap of the harness is attached, to hold back a carriage when going down hill, or in backing; also, the strap or part of the harness so used. [ 1913 Webster ]