My biggest pet peeve is the phrase "Lock and load" (how can one load a gun, once it has been locked?)
The phrase "Lock and load" did not exist until 1949, when Marion Morrison (better known as John Wayne) had immortalized it in the movie "Sands of Iwo Jima." The "Duke" was supposed to say, "Load and lock" but erred and said, "Lock and load, boy, lock and load."
To "Load and lock" refers to the operation of the M1 Garand Rifle, a standard WWII army rifle, where one would load a single round into the Garand, and then strike the bolt handle with the heel of the hand thereby forcing a round into the chamber and ensuring that it was fully closed and locked into place.
You can find use to the phrase "Load and lock"in Gene Gach's 1942 movie, "In the army" where it's said, "One round, ball ammunition, load and lock!"
It was also used during the Spanish-American War. The Annual Reports of the War Department shows a dispatch from the Philippines on June 15th 1899, which reads: "The line was under strong long-range fire and the order was given to load and lock the pieces; investigation proved that the white objects seen were the marines returning to their ship."
The term "lock and load" is commonly used now as a reference to being prepared for an impending incident.