But as it seems is the name of a mountain, I would suggest that it comes from roche déboule, meaning that rock are tumbling down from the top, which later turned to "Roche De Boule"
Des Des is short for the youtuber's name Destery, Destery Moore to be in fact! he calls him self Capn Des Des. you know, because Destery starts with Des DEStery DESDES! haha yeah thats what desdes...