If we want a name to fully describe the concept it points to, then it must be a very simple concept indeed. ​ But we still have to explain what a Mappable is. “What’s a Mappable? Well, it’s something you can map over!” is a terrible explanation! It’s literally just the grammatic expansion of the word. All it does is move the question one bit further ​ Functor is hard to learn. It is not hard to learn because it is named Functor. If you renamed it to anything else, you’d have just as hard of a time, and you’d be cutting off your student from all of the resources and information currently using the word “functor” to refer to that concept.

Trying to come up with a grand theory about what makes a good pet name. What are your favorites? (Recently, I met a Pomeranian named Potato and it was ideal for reasons I can't fully identify.)— Rowan Hisayo Buchanan (@RowanHLB) May 16, 2019

I can’t be the only one who has to stop and think which “direction” filter() goes. Am I filtering in or out?