Simplify the following text for a Grade 12 native English-speaking person.
Original: 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 .
Simplified: 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 .