Okay, rave time.
Not that kind of rave. Put down the glow sticks.
Rave first showed up in the early fourteenth century as a word for someone showing signs of madness. It comes from the Old French raver, a variant of resver, which means either to dream or to be crazy. Before that, no one knows where it came from. Though it seems like they would fit together, ravage is not related to rave. Ravage comes from the Old French word ravage, destruction, and ravir, to take away. There’s also ravish, which comes from ravir as well, as does the word rapid, meaning rave is quite alone in the etymological word.
University of Texas at Austin Linguistic Research Center