Arsaces I (=Parthian Arshak) in Wikipedia

Arsaces is the eponymous Greek form of the dynastic name (rather than the personal names of the kings) adopted by all epigraphically attested rulers of the 'phil-hellenenic' Arsacid dynasties. The indigenous Parthian and Armenian form was Arshak.

Read More about Arsaces I (=Parthian Arshak) in Wikipedia