Perhaps it comes from avionics lingo. Mostly fighter integrated avionics.http://www.ausairpower.net/TE-F-111-Upgrades-1998.html
Typical radar targeting is wholly integrated, the user need only put the crosshairs on the intended aimpoint in the radar image, and squeeze a button to lock it in.
(...e apertar um botão para o radar "travar" no alvo - ou o sistema de armas "travar no alvo".)
In a way, it got synonymous with "that you are sure of something", as today people rely on technology.