The pump action sound comes from the real operation of a pump-action shotgun, where sliding the fore-end ejects a shell and loads the next round. Film and game sound designers have used that distinctive racking noise for decades as shorthand for armed readiness because audiences learn to associate it with an imminent threat. Online, the isolated clip spread through soundboards and editing packs, where its sub-second length makes it easy to drop into memes, trailers, gaming montages and short videos without any dialogue or music.