The sound comes from Call of Duty: Modern Warfare 2, where it signals that a player has called in a tactical nuke, ending the match in a blinding blast. Players recognised the siren instantly, and clips of it began circulating as a standalone warning sound long after the game's peak. It later spread through gaming edits, reaction videos and prank clips, where the familiar alarm instantly tells viewers that something catastrophic, or deliberately exaggerated, is about to happen. Its recognisability keeps it useful for creators who want instant tension without explanation.