There was an article I recently read about how the .cat domain name came about. The summary for those not familiar is that this is an official language domain extension for the Catalan language. There are several of these domains but when it was created, it was unheard of and had the currently rancid government of PP been in power at the time, it would never have come about.
Being the pedantic nerd that I am, I called out the Washington Post on the fact that they used the term Catalonian instead of Catalan to refer to the people which meant that author and at least one editor made the mistake. You won’t of course see this in the article now as they fixed it without naturally mentioning that they originally had it wrong; go go quality journalism…
So why is it Catalan and not Catalonian? After all, it’s Catalonia in English so “Catalonian” would seem correct, no? Sure, someone from Italian is an Italian, but someone from Portugal is not a Portugalian. It’s just a fact that the demonym of a people doesn’t always follow a logical path in English such as myself, I’m from California and thus an “Intolerable Twit”. The English should be exceptionally mindful of this as I would have never guessed that someone from Manchester is a Mancunian–come again?
How did this come about? No one is fully sure although it’s thought to come from French like all illogical aspects of English. This is due to the French inheriting their word for the Catalan people from the nearly-extinct Occitan language which itself was extremely similar to the Catalan language. Had this not happened, I can only assume that it would have become catalain, maybe? And it’s true that it does break with generally-thought conventions even in Castilian where it’s catalán but then valenciano to mean someone from Valencia.
In case you need more evidence (and while this is no scientific system) a search on Google for “Catalan people” brings up about 28 million results. “Catalonian people” brings up about half a million and honestly should be accompanied by a solid smack to ones head for thinking that was correct in the first place.