Iran, Imperium Persia Raya al Majusi Part 1
The name “Irān“, meaning “land of the Aryans”, is a new Persian of the old genitive plural aryānām (proto-Iranian, meaning “of the Aryans”), first attested in the Avesta as airyānąm (the text of which is composed in Avestan, an old Iranian language spoken in northeastern Greater Iran, or in what are now Turkmenistan and Tajikistan). The proto-Iranian term aryānām is present in the term Airyana Vaēǰah, the homeland of Zoroaster and Zoroastrianism, near the provinces of Sogdiana, Margiana, Bactria, etc., listed in the first chapter of the Vidēvdād, immediately after it. The Avestan evidence is confirmed by the Greek sources: Eratosthenes apud Strabo speaks of Arianē as being between Persia and the Indian subcontinent.
Although, up until the end of the Parthian period in the 3rd century C.E, idea of “Irān“ had an ethnic, linguistic, and religious value, it did not yet have a political import. The idea of an “Iranian“ empire or kingdom in a political sense is a purely Sasanian one. It was the result of a convergence of interests between the new dynasty and the Zoroastrian clergy, as we can deduce from the available evidence. This convergence gave rise to the idea of an Ērān-šahr “Kingdom of the Iranians,” which was “ēr“ (Middle Persian equivalent of Old Persian “ariya“ and Avestan “airya“).