Luba-Kasai is a Bantu language spoken in the Democratic Republic of the Congo, where it is a national language, along with Lingala, Swahili, and Kikongo. It is one of two major Congolese languages called "Luba" . The prefix Tshi/ or Ci followed by the suffix Luba, comes to mean 'of the lubas' or language of the baluba or even the speaking of the baluba. Wikipedia
D.R. Congo