The line comes from Team Fortress 2, Valve's class-based shooter released in 2007, where the Soldier is the rocket-wielding American patriot voiced by Rick May. His shouted Fire is one of several battle cries triggered when attacking, and it became a staple of TF2 meme culture through Source Filmmaker animations, Garry's Mod videos and YouTube edits. Creators still reach for it because the delivery is instantly recognisable even to people who never played the game, making it a handy comic cue for any launch or attack moment.