Fetter fet'-er:
Found only in the plural in both Old Testament and New Testament; fetters of iron (Psalms 105:18, Psalms 149:8; so probably Mark 5:4, Luke 8:29) or brass (Judges 16:21, 2 Kings 25:7) were frequently used for securing prisoners.
See CHAIN.
Figurative: of trouble (Job 36:8).