Sure! If you want a general answer you can look up endonyms and exonyms on wikipedia but if you want specifics for Persian i’ll write something short here. The correct form of the word is Persian because it is the one which English-speakers are and were more familiar with due to its long history. It basicly goes a couple thousand years back and correctly signifies the history of the language within the English-speaking mind As language of the people who lived in Iran (which was called Persia until the last century). Etc. However, with the mass immigration of Iranians to other countries and their unawareness of how endonyms and exonyms work, they started claiming their language is called Farsi, the word which is used to refer to the language in Persian, instead of Persian, which was word English-speakers used. Which incorrectly cuts the Persian language from its history and makes it appear as a newly built language since there are no mentions of it before the current century. This was intensified by the Iranian diaspora in Los Angeles or US in general, which doubled down on their stupidity to build a new identity since thay no longer had connection with their own. Keep in mind that this is in no way a complete explanation. There’s a lot more to this. Enough to write a book. But this is the overall gist of things. Hope it helps!