Zanj (Arabic: زنج; "Land of the Blacks" or "Land of the Negroes") was a name used by medieval Arab geographers to refer to both a certain portion of the coast of East Africa and its inhabitants, Bantu-speaking peoples called the Zanj. The seaboard is also the origin of the place-name "Zanzibar".
Read more about Zanj: Division of East Africa, History of Zanj, Arab Views On The Zanj, Zanj Rebellion