I tend to agree with Tim. This knife 'looks' more like a Congolese dagger. But I have no idea of its origin (tribe).
I have a small Shona dagger in my collection. The construction of this knife is quite different. The blade sits much deeper into the handle.
The blade of the mystery dagger is firmly fixed and never 'sat' deeper into the handle.
On the other hand, the handle of this small Shona knife also has carvings on one side only.
Here are some other pics.