The riff comes from Seinfeld, the American sitcom that ran through the 1990s and used short slap bass passages to move between scenes instead of a traditional theme song. Those transitions became part of the show's identity through syndication and reruns, and later through short clips shared online. Editors began reusing the sound on its own to borrow that sitcom feel, and it stuck because listeners recognise it instantly even without seeing the show. Today it works as shorthand for an awkward pause, a time jump, or a joke landing badly.