The callout comes from Left 4 Dead, Valve's 2008 co-op shooter, where survivors automatically shout the name of a Special Infected when they spot it. The Smoker is a tall infected that drags players from a distance with its long tongue, so hearing the warning meant a teammate could be pulled away seconds later. Clips of the shout later spread through gaming videos, streams and soundboards, where it became a reusable alarm for ambushes, lurking enemies and anyone quietly waiting to strike.