Each time I've read Les Misérables, I've had a greater appreciation for the chapter on argot. The first time I skipped it. The second time I decided I hadn't missed much. The third time I could see what Hugo was doing thematically: https://www.hyperborea.org/les-mis/book/slang/
The latest episode of the Les Mis Reading Companion is on that chapter, and they give it even more context, illustrating how language can be used for gatekeeping...or rebellion. https://readlesmis.libsyn.com/ep39-iv7i-iv-argot