What is "sumu-abum"

Sumu-Abum (also Su-abu) was an Amorite, and the first King of the First Dynasty of Babylon (the Amorite Dynasty). He reigned from 1894-1877 BC (middle chronology). He freed a small area of land previously ruled by the fellow Amorite city state of Kazallu which included Babylon, then a minor administrative center in southern Mesopotamia. Sumu-Abum (and indeed the three Amorite kings succeeding him) makes no claim to be King of Babylon, suggesting that the town was at this time still of little importance.