Explode began in a Roman theatre. Explodere meant to drive a performer off the stage by clapping, ex- and plaudere, to clap, so a bad actor was clapped out of the room by the same hands that clapped a good one into staying. Applaud comes from the same verb, pointed the other way. English took explode in the 1530s to mean rejecting something with scorn, and that sense still hangs on in an exploded theory, one that has been hooted off. Only near the end of the eighteenth century did the word start to mean bursting with a bang, probably because the noise was the part everyone remembered. It is the same sound either way. What it meant depended entirely on which direction you wanted the actor to go.