How did the earlier term Chari-Nile become replaced by Nilo-Saharan?

The term "Chari-Nile" was originally proposed by linguist Joseph H. Greenberg to describe a language family named after the Chari and Nile river watersheds where many of its constituent languages were located. This designation replaced his earlier term, "Macro-Sudanic," to better distinguish his grouping from the work of previous scholars.1

The Chari-Nile designation was eventually superseded by the term "Nilo-Saharan" following Greenberg’s 1963 study, which introduced a more comprehensive genetic classification of African languages. In this updated framework, the Nilo-Saharan family was established as a "superstock" that incorporated the earlier Chari-Nile family alongside several other language groups that had previously been considered independent or isolated. Consequently, the Chari-Nile label is now considered obsolete, as Nilo-Saharan provides a broader and more inclusive classification for these related languages.1