Jack-in-shackles

A giant ghostly creature from folklore Yorkshire, leaping out of the darkness at travelers. His approach can be heard by the ringing of chains.

The name "Jack" in the name of the creature (Jack-in-Iron), as in other similar cases (Jack-o-lantern, Jack-in-Green), does not indicate a proper name. Such names in the names usually indicate, rather, the uncertainty of the creature, and mean "some kind", referring only to the fact that the creature is male.