The ba dum tss comes from the rimshot, a drummer's joke cue in live comedy, vaudeville and cabaret-style shows, where a snare and cymbal marked the end of a gag. It moved into radio, television and cartoons as a shorthand for a punchline, then into online video, where editors use the same sting to signal irony or a deliberately corny joke. Its staying power comes from instant recognition: even without a stage or a laugh track, listeners know a joke has just landed.