Clarification Request: "Piltovian" or "Piltovan"?

So, a while back things were spelled out fairly clearly as the correct term being "Piltovian". I can't remember the specific post, although I believe it was something from Kitae. However, a lot of the newer text seems to say "Piltovan". Admittedly I think both could be understood to be correct, sort of like "aluminum" and "aluminium". After all, we use "Noxian" for things pertaining to Noxus, when we could just as easily call them "Noxan". Perhaps Demacian dialects use "Piltovian" and Noxian dialects use "Piltovan".

Either way, it would be nice to get a little clarification on this, if there is indeed a "correct term" being used.