What is "peiros"

The Peiros is a river in the central and the northwestern parts of Achaea, Greece. The river is known locally under several names including Kamenitsa (Καμενίτσα), Mellas (Μέλλας), Pieros (Πίερος), Nezeritiko (Νεζερίτικο), Prevedos (Πρέβεδος) and Acheloos (Αχελώος). One of its tributaries is the Tytheus, also known as Parapeiros.