As a political term, Babylonia became current during the Kassite period when it was also known by its Kassite name Karduniash. It comprised the area south of the Jezirah up to the marshes of the Persian Gulf, bordered to the east and west roughly by the Tigris and Euphrates rivers but with no clearly defined boundaries. In modern works, Babyloniais also used as a topographic term, more or less synonymous with southern Mesopotamia, in distinction to Assyria or northern Mesopotamia.
Historical Dictionary of Mesopotamia. EdwART. 2012.