Kick over the traces

Means to cast off restraint, authority or control and derives from the leather harness or traces to which a horse is attached when harnessed to a vehicle. The traces are attached to the horse’s collar on either side and in turn are attached to the vehicle. If a horse were to rear up and kick over the traces it would break free from its restraining harness. Its figurative meaning of breaking free of restraints dates from the mid-19th century.