I see how these double names can be confusing. Persia has always been called Iran by Iranians (Persians). The fact that Latin based languages know Iran as Persia, is because they'd called Iranians by the language they were speaking, also a sect that were part of the initial founders of Iran, named Pars. Their language, being Parsi, was Latinized as Persian and so the continent including almost all the Middle East was called Persian Empire. Of course after Arab invasion of Iran, since they don't have the sound "P" the race was called Fars, instead of Pars and the Language was called Farsi, which is what's called today commonly by all. Quite an accomplishment that we still speak Persian if you ask me after not being allowed to speak our language for 200 years after Arab invasion. But the country has always been called Iran and that's how it has been referenced to in our ancient literature. I suspect it has been named after Aryans who immigrated to Iran from North and were the first founders of this country. This is not the only name that's been latinized, I mean you call him Cyrus, we call him Koorosh. You call him Xerxes, we call him Khashaayaar.