(noun) A short strap fastened around the leg of a hawk or other bird used in falconry.
(verb) To put jesses on.
Etymology: old French jet, something thrown
Last year I stumbled across a barn sale that had a box of free items, including a frog song identification cassette tape and a well-worn pair of jesses. I took the frog tape and left the falconry equipment. Tough call, but I have a cassette player, and I don't have a falcon.