The term ''Sawad'' was also used in early Islamic times for the region of the alluvial plain of the Tigris and Euphrates rivers, contrasting it with the arid Arabian desert. As an Arabic word,  means "hem", "shore", "bank", or "edge", so that the name by folk etymology came to be interpreted as "the escarpment", viz. at the south and east of the Jazira Plateau, which forms the northern and western edge of the "al-Iraq arabi" area.