An old-fashioned swivel, orig, OFr: vervelle = joint 
• (n.) In falconry, one of the rings secured to the ends of the jesses.
Var'vel noun [ French vervelle .] In falconry, one of the rings secured to the ends of the jesses. [ Written also vervel .] 
A less used piece of equipment. This flat silver or brass ring served several purposes. It was attached at the end of a long slitless jess as the attachment for the leash, but also served as the quick release mechanism when hunting. (A single strip of leather or rope could be attached to the glove, passed through the rings, and held by the falconer...
metal ring attached to hawk's jess that connects to a leash