Lucy Mair in “Marriage and Family in the Dedza District of Nyasaland,” Journal of the Royal Anthropological Institute 81 (1-2), 1951, (p. 103) reports on the pragmatic functioning of descent names among Bantu-speaking Ngoni and Cewa.
Not only are they used vocatively, as one would expect, in the respect register but also, conversely, in playful address to small children. Typically, cross-linguistically, older and younger relatives are treated differently: older relatives are addressed using respectful forms, while younger children are addressed using familiar forms. For instance, children can often be addressed by their personal names, while they in turn must use kinship terms when addressing adults. But there’s a known property to kinship terms whereby in some cultures (Arabic, Georgian, Hopi, see The Genius of Kinship, pp. 156-157, for a more complete roster) adults and children within the same family reverse their normative kinship terms in direct address to each other, so that a child becomes “father,” “mother,” “grandfather,” “grandmother,” “uncle,” or “aunt” to a corresponding adult, and the other way around. It seems that among the Ngoni the use of a descent name in playful interactions with children belongs to the same category of pragmatic phenomena. It may function as an educational device, so that children learn descent names from an early age, or as a restricted relaxation of verbal prescription and taboos in specialized playful contexts.