Akkad is the historical name of a region in northern Mesopotamia around the city of Akkad, probably near the confluence of the Diyala with the Tigris. After the emergence of the Akkadian Empire, Akkad came to designate the area between Nippur and Sippar. During the first millennium BCE, Akkad was used as a name not only for the northern half of Babylonia, but also for Sumer. The meaning of the name is unknown.