The root name "''Afghān''" is, according to some scholars, derived from the Sanskrit name of the ''Aśvakan'' or ''Assakan'', ancient inhabitants of the Hindu Kush region. ''Aśvakan'' literally means "horsemen", "horse breeders", or "cavalrymen" (from ''aśva'' or ''aspa'', the Sanskrit and Avestan words for "horse"). Historically, the ethnonym ''Afghān'' was used to refer to ethnic Pashtuns. The Arabic and Persian form of the name, ''Afġān'', was first attested in the 10th-century geography book ''Hudud al-'Alam''. The last part of the name, "''-stan''" is a Persian suffix for "place of". Therefore, "Afghanistan" translates to "land of the Afghans", or "land of the Pashtuns" in a historical sense. According to the third edition of the ''Encyclopedia of Islam'':