Whilst re-reading Dierk Lange's A Sudanic Chronicle: The Borno Expeditions of Idris Alauma (1564-1576) According to the Account of Ahmad b. Furtu, we were reminded of the Binawa convert, Nasr Bultu. Close ties between him and the vizier of Idris b. Ali of Borno (r. 1564-1596), Kursu b. Harun, also an Ngizim according to Lange, were also indicated by Nasr's Islamic conversion. Presumably, this is why Nasr Bultu began to use an Islamic name like Nasr. However, each of his appearances in Ahmad b. Furtu's chronicle include the surname Bultu.
We wonder if this surname is actually the Kanuri word for hyena, búltu (Cyffer's spelling). In the Ngizim-English dictionaries easily found online, that language's word for hyena is not like the Kanuri term. For instance, the dictionary affiliated with the Yobe Languages Research Project lists bədlamu (see the Ngizim-English-Hausa Dictionary by Mohammed Alhaji Adamu and Usman Babayo Garba Potiskum). Intriguingly, the Hausa language does have the word bultu for a type of hornbill, possibly pointing to a Hausa connection for Nasr Bultu's surname. Since the Binawa were part of the Western Ngizim, a possible Hausa-derived word used for a name was perhaps plausible?
However, the closer ties of Nasr Bultu to Borno and one of its top officials during the reign of Idris Alooma could have played a greater role in the Binawa leader's new name. If one theorizes that his surname was also new like his first name of Nasr, perhaps the Kanuri-derived word was another sign of the integration of non-Kanuriphone populations into Borno. Islam and Islamic-derived names were an important part of that process. But, adding Kanuri names or surnames could have been yet another layer of the role of culture and language in integrating other ethnic groups into the state. Why the name of an animal may have been adopted as a surname is not clear, either, although it may have ties to the depiction of the hyena in Kanuri folklore and oral literature.