Is it ensure, insure, or assure?
late 15c., from mouse (n.) + trap (n.). Figurative use from 1570s. The thing is older than the word. Old English had musfealle; Middle English had mouscacche (late 14c.).
A small, inferior theater or nightclub: He walked out on the stage of a mousetrap called the Blue Angel (1950s+)
To trick someone into a trap, esp by various feints (1950s+ Sports)