The sound comes from Team Fortress 2, Valve's team-based shooter released in 2007, where the Spy class uses a watch to turn invisible and slip past enemies undetected. The cloak effect has been part of the Spy's toolkit since the game's early years, making it familiar to millions of players who learned to listen for it as a warning. Outside the game, the clip spread through gameplay videos, montages and short-form edits, where it now signals stealth, trickery or a sudden disappearance even for viewers who have never played TF2.