Ray Belli is amazing and I've failed to learn so many things from his podcast because as soon as he starts speaking my mind wanders. It's like the audio version of reading the same paragraph four times because my brain decides to think about something else while my eyes move across the page
Dutch is such a weird one. We don't call ourselves "Dutch" in Dutch, we call ourselves "Nederlands". This would be something like "Netherlandish" in English. We do call Germans "Duits" though, and they call themselves "Deutsch". Somehow in English German and Dutch got a bit messed up. The reason is probably that during the middle ages we did refer to our language as "Dietsch", so that probably stayed around.
Dutch is the English name for the dominant language of the Netherlands, and in English we often name people after their language. The Netherlands is also called Holland in English, even though Holland is just the most economically-dominant sub-region of the Netherlands, and the location of its main trading ports, rather than the whole country. Which makes sense if you are an English sailor who only knows the Netherlands through its trading ports and has little need to go inland.
But we also don't call our language "Dutch", we call it Nederlands. It's a relic of an old time, but actually German should be called Dutch and Dutch should be Netherlandish. It'd help a lot with the confusion of young German and Dutch people learning English for the first time haha. Would also resolve the confusion around "Pennsylvanian Dutch" being German.
Oh there's plenty of rules, and if you follow them you'll be wrong because each rule has 20 exceptions you have to memorize because English isn't a language, it's several languages in a trench coat.
FYI, there's a little debate over this in the English language, but many would say that the proper demonyms are Afghan for the Pashtun ethnic group, and Afghanistani (or rarely Afghanese) for people from Afghanistan regardless of ethnicity.
Afghani is their currency.
I believe it comes from a discrepancy between the Persian and Pashto languages. Afghani being the correct term in Persian, and Afghan being the term in Pashto.
Afghani is pretty widely used in English, and even appears in some dictionaries, but many argue that it's not correct.
So a person is an Afghan, they eat Afghan food, wear Afghan clothing, have Afghan customs, and their currency is the Afghan Afghani (in case some other country ever adopts a currency called the Afghani and you need to differentiate between them)
When I was a kid our family went on vacation to the US. Everyone kept asking if I was Dutch, which I thought was German (Deutsch).
So I kept correcting them, saying I was Netherlandish :)