@red_bean_casserole uhhh. From a quick search it says Nukeru and it means "to extract" or "Fall out" or "Release". Maybe in context of rubbing out it means extracting or letting out by intense rubbing (masturbation to release semen?) Idk
@red_bean_casserole , @Umesan It's probably the same root as the "nuki" used here, though I don't have the raws to check. If it is, then it does seem to be a euphemism for masturbation.