trace 2 
(trās)
(trās)n.
Idiom: 1. One of two side straps or chains connecting a harnessed draft animal to a vehicle or whiffletree.
2. A bar or rod, hinged at either end to another part, that transfers movement from one part of a machine to another.
kick over the traces
To act in a way that contravenes social expectations or propriety: "As soon as the opportunity presented itself, [he] kicked over the traces and threw himself into a life of pleasure" (K.D. Reynolds).
[Middle English trais, from Old French, pl. of trait, a hauling, harness strap, from Latin tractus, a hauling, from past participle of trahere, to haul.]