Middle Persian is the Middle Iranian language\/ethnolect of Southwestern Iran that during Sassanid times ( 224-654 CE ) became a prestige dialect and so came to be spoken in other regions as well . Middle Persian , indigenously known as `` PÃ cents rsig '' sometimes referred to as Pahlavi or Pehlevi , is the Middle Iranian language\/ethnolect of Southwestern Iran that during Sassanid times ( 224-654 CE ) became a prestige dialect and so came to be spoken in other regions as well .