early 14c., "a support for something," from Old French trestel "crossbeam" (12c., Modern French tréteu), presumed to be an alteration of Vulgar Latin *transtellum, diminutive of transtrum "beam, crossbar" (see transom). Specific meaning "support for a bridge" is recorded from 1796.[trestle etymology, trestle origin, 英语词源]