The Greek noun desmon refers to a bond, chain, or fetter — something that physically restrains a person. In the New Testament it appears in descriptions of the demon-possessed man (Mark 5:4; Luke 8:29), of John the Baptist's imprisonment, and frequently in Paul's prison letters. It also occurs in the metaphorical sense of the 'bond of the Spirit' (Ephesians 4:3) and the cords of sin.
The imagery of bonds and chains runs throughout the New Testament. Jesus came to 'set at liberty those who are oppressed' (Luke 4:18) — to break every chain of sin, death, and Satan. The demon-possessed man of Gerasa could not be held by any desmon (Mark 5:4) — yet was instantly liberated by a word from Jesus. Paul's desma (chains) in prison are paradoxically instruments of gospel advance (Philippians 1:12–14). Ultimately, Revelation 20:1–3 depicts Satan himself being bound with a great chain — the ultimate desmon, applied by divine authority to the great enemy of souls.