Kaabu from historical narrations means Kaa Bun (to stone or throw). This is in reference to the throw of spears, bow and arrows. Kaabu is also a direction for North. Tilibo is East, Tiligii for West and Niano for South.
Kaabu is as Mandinka as it can be. Actually, the Kaabunkas in those days will not name their command centre with any other language, bearing in mind, settlements like Bere Kolon, Sama etc were typical names etched in the languages. The Fula territories are referred to as Fuladou or Futa. This was never an issue. To remotely manufacture stories about places and events is terribly immature.
Similar name derivatives can be found in the Gambian currency:
Dalasi (Da La So) to sew a costume for wrestlers. The underlining meaning is rooted in the difficult task of wrestling.
Cassamance (Caa Sama Caasii) to go settle at a place for farming.
The above are typical example of unique ethnic names associated to places and things. This can be found in Serere, Wollof, Jola, Fula etc.
It is incredibly haste to start making up stuffs about other people's history