Wikipedia
The Ikelan (Éklan/Ikelan or Ibenheren in Tamasheq; Bouzou in Hausa; Bella in Songhai; singular Akli) are a caste within Tuareg society, who were at one time slaves or servile communities. While the Ikelan now speak the same language as the Tuareg nobles and share many customs, they are of assimilated Nilotic origin rather than of Berber heritage like the ethnic Tuareg. They also often live in communities separated from other castes.
The Ikelan's situation is somewhat analogous to the Haratin within Maure society in the western Sudan. Like the Haratin, the name "Ikelan", and to a much greater degree Bouzou and Bella, are exonyms (a name not used by that people themselves) with negative connotations. Historically the term "Ikelan" has been used to refer to the black slaves of the Tuareg and the term iklan means "to be black" and these slaves provided labor at their masters request. In parts of West Africa an unknown number of Ikelan caste individuals continue to live in slavery or slavery like relationships with other Tuareg individuals. Ikelan individuals and communities are found through much of Niger, Mali, southern Algeria and Libya, and parts of northern Burkina Faso and Nigeria.