Why do Iranian people call their language "Farsi"? "Farsi" and "Persian" have the same origin, which are exonyms derived from the capital of Achaemenid dynasty, Perspolis.

I know Iran changed its English name from "Persia" to "Iran" since "Iran" is the endonym which Iranian people call themselves "Iranian".

Why do Iranian call their language as "Farsi" as an exonym instead?