Etymology

The term Iran (ایران) in modern Persian derives from the Proto-Iranian term Aryānām first attested in Zoroastrianism's Avesta tradition. Ariya- and Airiia- are also attested as an ethnic designator in Achaemenid inscriptions. The term Ērān, from Middle Persian Ērān (written as ʼyrʼn) is found on the inscription that accompanies the investiture relief of Ardashir I at Naqsh-e Rustam. In this inscription, the king's appellation in Middle Persian contains the term ērān (Pahlavi ʼryʼn), while in the Parthian language inscription that accompanies it, the term aryān describes Iran. In Ardashir's time, ērān retained this meaning, denoting the people rather than the state.
Notwithstanding this inscriptional use of ērān to refer to the Iranian peoples, the use of ērān to refer to the geographical empire is also attested in the early Sassanid period. An inscription relating to Shapur I, Ardashir's son and immediate successor, includes regions which were not inhabited primarily by Iranians in Ērān regions, such as Armenia and the Caucasus." In Kartir's inscriptions the high priest includes the same regions in his list of provinces of the antonymic Anērān. Both ērān and aryān comes from the Proto-Iranian term Aryānām, (Land) of the (Iranian) Aryas. The word and concept of Airyanem Vaejah is present in the name of the country Iran (Lit. Land of the Aryans) inasmuch as Iran (Ērān) is the modern Persian form of the word Aryānā.
In the outside world, the official name of Iran from the 6th century BC until 1935 was Persia or similar foreign language translations (La Perse, Das Persien, Perzie, etc.). In that year, Reza Shah asked the international community to call the country by the name "Iran". A few years later, some Persian scholars protested to the government that changing the name had separated the country from its past, so in 1959 Mohammad Reza Shah announced that both terms could officially be used interchangeably. Now both terms are common, but "Iran" is used mostly in the modern political context and "Persia" in a cultural and historical context. Since the Iranian Revolution of 1979, the official name of the country has been the "Islamic Republic of Iran."