Sawad was the name used in early Islamic times (7th-12th centuries) for southern Iraq. It means "black land" or "arable land" and refers to the stark contrast between the alluvial plain of Mesopotamia and the Arabian Desert. Under the Umayyad and Abbasid Caliphates, it was an official political term for a province encompassing most of modern Iraq except for the Syrian Desert and Upper Mesopotamia in the north.
As a generic term in Arabic and Persian, saw?d (?) was used to denote the irrigated and cultivated areas in any district. Unmodified, it always referred to southern Iraq, the saw?d of Baghdad. It replaced the earlier and more narrow term R?dh?n.