The sound comes from Half-Life, Valve's influential first-person shooter first released in 1998, where the player can toggle a flashlight to explore dark areas. The short toggle click became part of the game's everyday audio language, instantly signalling light and darkness to players. As Half-Life clips, mods and later Counter-Strike footage circulated online, the tiny sound was lifted for short soundboards and video edits. It survives because it is instantly recognisable to FPS players and works as a clean, unambiguous switch sound in almost any scene.