The cha ching sound comes from mechanical cash registers invented in the late 1800s, whose bells rang when the drawer opened to signal a sale and discourage theft. That ringing and coin rattle stayed in shops, cartoons, games and adverts for decades, becoming a universal shorthand for money earned. Online, creators borrowed the short register recording for tip alerts, haul videos and memes about getting paid, and its two second length makes it easy to drop into edits without covering speech or music.