What is "tytheus"

Tytheus or Tythefs is a river in the western part of Achaea, Greece. The river is also known as Parapeiros (Παραπείρος), and was known as Toskesi (Τόσκεσι). The Tytheus river begins in the western part of the Erymanthos mountains. It passes through the municipalities of Tritaia and Fares. It empties into the river Peiros near the village Agios Stefanos.