The line comes from Call of Duty multiplayer, where team announcers call out enemy killstreaks so players can react. In Modern Warfare the cruise missile is a player controlled streak that can wipe a grouped team, which made its warning one of the most feared callouts in the match. Clips of the audio spread through gaming edits and soundboards because the phrasing is instantly recognisable to shooter fans. It remains popular as a shorthand for any incoming threat that cannot be stopped.