Both Iraq
With the two Iraq ( Arabic العراقين, DMG al-ʿIrāqain ) in the Islamic Middle Ages the double region Iraq and western Iran (without the province of Fars - Persis , but including the area around today's Tehran) was referred to.
This designation suggested that there was an Arab Iraq to the west of Shatt al-Arab ( Arabic عراق العرب, DMG ʿIrāq al-ʿArab ), today's Republic of Iraq , and east of it a Persian or non-Arab Iraq ( Arabic عراق العجم, DMG ʿIrāq al-ʿAǧam , cf. adscham ), the ancient province of Djibal . In the state name of the Kingdom of Iraq , founded in 1921, the attribute Arabic was dispensed with, possibly out of consideration for the Kurdish population as the second state people.
Until the fall of the Abbasid - Caliphate in the conquest of Baghdad in 1258 in the Mongol invasion , at least the inhabited part of Arabs, now belonging to Iran region on the eastern side - in fact, both banks were Khuzistan - always under common rule. So was z. B. reported from Iraqi Buyids and Iraqi Seljuks , but meant the rulers of Rey , Hamadan , Isfahan etc.
See also: Both Sicilies , Both Rome