Originated in American English, supposedly as an instructional command to prepare an M1 Garand, the main rifle used during World War II, for battle, though it is disputed if the phrase was actually used this early. It was used in 1949 by John Wayne in the movie Sands of Iwo Jima. Various similar phrases predate it, including in transposed form as “load and lock”.
- (US, slang) A command to prepare a weapon for battle.
- (US, slang) Prepare for an imminent event.