In contemporary English, there are major suffix groups for languages, each tend to predominate a geographic region. the most common is "-an" such as German, Italian, Russian, etc. This is found globally but tend to predominate in Europe and Africa. The "-ish" is also very common, eg. English, Spanish. The "-ese" group tend to be predominant in Asia, eg. Chinese, Japanese. Then there's the "-i" group, eg. Hindi, Bengali. There are more, but you get the picture. This did not even include ones without suffices such as French and Greek.

Along the same note, how did the national or ethnic terms develop? Eg. why are people from Israel called Israelis and not Israelians?