shackle

1. A restraint fitted over a human or animal appendage, such as an ankle, finger, or wrist, normally used in a pair joined by a chain. · The prisoner lay in shackles in his gloomy cell.
2. A U-shaped piece of metal secured with a bolt or pin across the ends, or a hinged metal loop secured with a quick-release locking pin mechanism, used for attaching things together while allowing for some degree of movement; a clevis.
3. Part of a padlock that consists of a loop of metal (round or square in cross section) that encompasses what is being secured by the lock.
4. A hook, ring, or other device for connecting, holding, lifting, etc.; specifically (nautical), a small incomplete ring secured with a bolt across the ends, used to connect lengths of cable or chain together, or to keep a porthole closed.
5. Synonym of hobble or hopple (“a short strap tied between the legs of a horse, allowing it to wander a short distance but not to run off”).
6. A link for connecting railroad cars; a draglink, drawbar, or drawlink.
7. A restraint on one's action, activity, or progress. (figuratively)
8. A length of cable or chain equal to 12½ fathoms (75 feet or about 22.9 metres), or later to 15 fathoms (90 feet or about 27.4 metres).

Plural shackles