Historically, it was commonly used in connection with non-Iranic peoples living within the Iranic cultural sphere, especially during the early and middle-Islamic periods such as Arabs, and various Turkic peoples (such as the Seljuqs and Ghaznavids).
In modern times, it is often used in connection with non-Persians such as Azeris,Kurds, and Baluchis, as well as non-Iranians living in Iran such as Arabs and Turkmens.
The Abbasids (after 750) established their capital in Iraq, eventually at Baghdad. A shift in orientation toward the east is discernible, encouraged by increased receptiveness to Persian cultural influence and the roots of the Abbasid revolution in Khorasan
It is argued sometimes that modern Iranian nationalism was established during the Pahlavi era, based on the aim of forming a modern nation-state. What is often neglected is that Iranian nationalism has its roots in the pre-Pahlavi era of the early 20th century. On the eve of World War I, pan-Turkist propaganda focused on the Turkic-speaking lands of Iran, Caucus and Central Asia. The ultimate purpose of persuading these populations to secede from the larger political entities to which they belonged and to join the new pan-Turkic homeland. It was the latter appeal to Iranian Azerbaijanis, which contrary to Pan-Turkist intentions, caused a small group of Azerbaijani intellectuals to become the strongest advocates of the territorial integrity of Iran. After the constitutional revolution in Iran, a romantic nationalism was adopted by Azerbaijani Democrats as a reaction to the pan-Turkist irredentist policies emanating from modern Turkey and threatening Iran’s territorial integrity. It was during this period that Iranism and linguistic homogenization policies were proposed as a defensive nature against all others. Contrary to what one might expect, foremost among innovating this defensive nationalism were Iranian Azerbaijanis. They viewed that assuring the territorial integrity of the country was the first step in building a society based on law and modern state. Through this framework, their political loyalty outweighed their ethnic and regional affiliations. The adoptions of this integrationist policies paved the way for the emergence of the titular ethnic group’s cultural nationalism.
According to Tadeusz Swietochowski, in 1930s, the term was used to describe the official policy pursued by Reza Shah Pahlavi to assimilate the ethnic minorities in Iran (Iranians as well as Non-Iranians). In particular, within this policy the Azerbaijani language was banned for use on the premises of schools, in theatrical performances, religious ceremonies and in the publication of books. Swietochowski writes:
Further east and as a result of centuries of foreign, Central Asian rule, India quickly adopted/assimilated several Persian cultural features, including column-based architecture (especially employing Persian-style colonnades and decorations for the columns themselves). More importantly, the Achaemenids' use of Aramaic as the official language of the Empire and their use of its associated script reintroduced writing to the Asian subcontinent. Both the Kharosthi and Brahmi scripts for writing Sanskrit and the various Prakrits are believed to derive from the Persian standard Aramaic script; Brahmi eventually developed into all of the scripts of modern India.
Persian vocabulary found its way into the Hindustani dialects of the Indo-Gangetic Plain, leading to a standard language known as Khariboli. An alternate name for Khariboli, Urdu, was later appropriated for the heavily-Persianized register of Hindustani; Urdu then became the chief official language of the modern Islamic Republic of Pakistan upon independence in 1947. As in post-independence India Persian culture and vocabulary was strongly associated with outside influence in general and Islam in particular, Indian and Hindu nationalists developed a Sanskritized and de-Persianised register of Khariboli which they named Hindi and made an official language of India in 1947. Despite their efforts, however, certain Persian terminology remains in currency even in Standard Hindi, and colloquial Hindustani across northern India retains large quantities of Persian vocabulary dialectically and even idiolectically.