Шатт-эль-Араб
Middle Persian literature and the "Shahnameh" (written between 977 and 1010 AD) use the name "Arvand" for the Tigris, the confluent of the Shatt al-Arab. Iranians also used this name specifically to designate the Shatt al-Arab during the later Pahlavi period, and continue to do so since the Iranian Revolution of 1979.