Japanese word for Japanese

Many non-Japanese people probably won't know Nippon, but it's common knowledge that countries have different names and not just the ones in an English atlas. You don't need to be a "weeb" or an expert of any kind to know this. I've never studied German and even I know Germany is Deutschland in German.

And just because you're physically not near people who speak different languages doesn't mean you won't meet them online. People speak English here but it doesn't mean they're all from anglophone countries.