The ka-ching effect comes from the mechanical cash registers used in shops for decades, where a bell signalled that a sale had been rung up, and that association carried over into cartoons, adverts and sitcoms long before online video. Creators on YouTube, Twitch and TikTok now use the same short ding as shorthand for money changing hands, because viewers understand it instantly without context. It remains popular for donation alerts, unboxings and business content, where a single familiar sound can turn a routine transaction into a small moment of celebration.