Yeah, I wonder about calling it "addable" or "mergeable". But neither of those really captures the full generality of it - would you expect composing functions to count as "adding" or "merging"?
Good point. Though a good side effect is that when you see it used that way you "a-ha!", or you figure it yourself you feel smart. Something like "endoMonoid" doesn't immediately suggest these use cases either (unless you're a math buff) but if you get to the explanation you're just left with the feeling that this is what was intended all along, not a neat breakthrough.
