Swivel

swivel
1. (Science: mechanics) A piece, as a ring or hook, attached to another piece by a pin, in such a manner as to permit rotation about the pin as an axis.
2. A small piece of ordnance, turning on a point or swivel; called also swivel gun. Swivel bridge, a kind of drawbridge that turns round on a vertical axis; a swing bridge. Swivel hook, a hook connected with the iron strap of a pulley block by a swivel joint, for readily taking the turns out of a tackle. Swivel joint, a joint, the two pieces composing which turn round, with respect to each other, on a longitudinal pin or axis, as in a chain, to prevent twisting.
Origin: AS. Swifan to move quickly, to remove; akin to Icel. Sveifla to whirl, shake, svifa to ramble, to turn. See Swoop, and cf. Swift a reel, Swift.