mid-14c., "net to catch fish" (implied in trammeller "one who fishes with a trammel net"), from Old French tramail "fine-gauged fishnet" (13c.), from Late Latin tremaculum, perhaps meaning "a net made from three layers of meshes," from Latin tri- "three" (see tri-) + macula "a mesh" (see mail (n.2)). Meaning "anything that hinders" is from 1650s, originally "a hobble for a horse" (c. 1500). Italian tramaglio, Spanish trasmallo are French loan-words.
1530s, originally "to bind up (a corpse);" sense of "hinder, restrain" is from 1727, from trammel (n.), a figurative use from the literal sense "bind (a horse's legs) with a trammel" (c. 1600). Related: Trammeled; trammeling.