The Bantu languages descend from a common ancestor spoken near the modern Nigeria and Cameroon border, and their present distribution is the result of an expansion beginning perhaps four thousand years ago that carried speakers east and south across the continent over two millennia. Whether that was migration, the adoption of a language by existing populations, or both in different places, is argued, and the answer probably differs by region.
What travelled is partly recoverable. Reconstructed vocabulary points to farming, to pottery, to ironworking in the later phases and to particular crops, and religious terminology reconstructs alongside it: the ancestors as an active presence, a distant creator, and the categories of affliction and its diagnosis.
The consequence for the atlas is that entries as far apart as the Kongo of the lower Congo river and the Zulu of KwaZulu-Natal share terms and structures without sharing a religion. Kimbwandende Fu-Kiau's account of Kongo cosmology, written from inside that tradition, and Bengt Sundkler's study of the independent churches of South Africa describe two entirely distinct religious worlds whose vocabularies are recognisably related. That relation is a fact about language, and reading it as a fact about belief is the error this article exists to prevent.
Sources African Cosmology of the Bantu-Kongo: Principles of Life and LivingKimbwandende Kia Bunseki Fu-Kiau with Bantu Prophets in South AfricaBengt G. M. Sundkler