A Shackle

1. A restraint fit over a human or animal appendage, such as a wrist, ankle or finger. Usually used in the plural, to indicate a pair joined by a chain; a hobble.
2. A U-shaped piece of metal secured with a pin or bolt across the opening, or a hinged metal loop secured with a quick-release locking pin mechanism. Shackle - Wikipedia
3. (figuratively, usually in the plural) A restraint on one's action, activity, or progress.
4. A fetter-like band worn as an ornament.
5. A link for connecting railroad cars; a drawlink or draglink.
6. A length of cable or chain equal to 12.5 fathoms or 75 feet, or later to 15 fathoms.
7. Stubble