We don't have synonyms for bornu yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are born, borne and cornu.
(n) :
(historical) An independent kingdom (1380-1893), descended from the Kanem–Bornu Empire (700-1380), that covered much of modern Chad and parts of Libya, Niger, Nigeria, and Cameroon
(n) :
(historical) An independent kingdom (1380-1893), descended from the Kanem–Bornu Empire (700-1380), that covered much of modern Chad and parts of Libya, Niger, Nigeria, and Cameroon