Middle Persian

Middle Persian is the Iranian dialect of southwestern Khuzestan, Lorestan, Chaharmahal and Bakhtiari provinces in Iran. During the Sassanid times (224-654 CE) it became a prestige dialect. It came to be spoken in other regions as well. Middle Persian is classified as Western Iranian language. It comes from Old Persian and is the ancestor of Modern Persian. 
The native name for Middle Persian (and perhaps for Old Persian also) was "Pārsik". The word is the origin of the native name for the Modern Persian language.