Some language names are also the names of the people who speak that language, for example Russian, Norwegian, Italian, and German. But others are not, for example Dutch, French, English, and Spanish. In these examples, all the former words end with -an, and all of the latter do not, but I don't think that is important. I am wondering if there is a reason for this, or if it is just coincidence based on how adjectives are formed. Sometimes they are the same word; and sometimes they are not.
Also, I am aware that people do say "the English" and "the Spanish" and "the Dutch," but I don't hear it as often in casual conversation. It seems more common to say "an Englishman" or "a Spaniard" or "a Dutchman."
I tried looking this up multiple times, but I cannot even form the question in a way that produces the correct results in Google. And I apologize if my tags are wrong, as I could not find a decent tag either.