Fine Flavio
I was thinking like you...but I' found this pic from 1953 showing a KUBA dancer with a sword in a scabbard attributed generally to the LUBA !
Well it's not simple...The western Luba (kasayi) rae not far from the Kuba region, and in the kuba territory you have people with the name of Luba (according with Felix : see the map).
We have to find and old colonial man, who live in this place to know...before he dies...
Luc