HOLDBACK
Etymology
Noun
holdback (plural holdbacks)
restraint (act or result of holding back, device that restrains)
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 downhill, or in backing.
The strap or part of the harness so used.
Source: Wiktionary
Hold"back`, n.
1. Check; hindrance; restraint; obstacle.
The only holdback is the affection . . . that we bear to our wealth.
Hammond.
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.
Source: Webster’s Unabridged Dictionary 1913 Edition