Topic summary
Middle Persian language

Extracted from the Wikipedia article Middle Persian.
Name
Aside from Parthian, Aramaic-derived writing was adopted for at least four other Middle Iranian languages, one of which was Middle Persian. In the 3rd century CE, the Parthian Arsacids were overthrown by the Sassanids, who were natives of the south-west and thus spoke Middle Persian as their native language. Under Sassanid hegemony, the Middle Persian language became a prestige dialect and thus also came to be used by non-Persian Iranians. In the 7th century, the Sassanids were overthrown by the Arabs. Under Arab influence, Iranian languages began to be written in Arabic script (adapted to Iranian phonology), while Middle Persian began to rapidly evolve into New Persian and the name parsik became Arabicized farsi. Not all Iranians were comfortable with these Arabic-influenced developments, in particular, members of the literate elite, which in Sassanid times consisted primarily of Zoroastrian priests. Those former elites vigorously rejected what they perceived as 'Un-Iranian', and continued to use the "old" language (i.e. Middle Persian) and Aramaic-derived writing system. Numerous examples can be identified through the myriad of Middle Persian Zoroastrian scriptures, such as the Denkard, Shkand-gumãnig Vizār, and many more. In time, the name of the writing system, pahlavi "Parthian", began to be applied to the "old" Middle Persian language as well, thus distinguishing it from the "new" language, farsi. Consequently, 'pahlavi' came to denote the particularly Zoroastrian, exclusively written, late form of Middle Persian. Since almost all surviving Middle Persian literature is in this particular late form of exclusively written Zoroastrian Middle Persian, the term 'Pahlavi' became synonymous with Middle Persian itself.