Although several sources (e.g. al-Biruni) appear to have considered 'Arash' to be the origin of the name 'Arshak' (i.e. Arsaces), the name of the Parthian dynasty derives from a Parthian- or Eastern Iranian equivalent of 'Ardashir', i.e. 'Artaxerxes', specifically Artaxerxes II, who the Arsacids claimed to descend from.