Derivation of the Names of the Prefectures from Rivers Some of the prefectures are named after the various rivers flowing across the land of Chad. Mayo-Kebi region was named after the river Mayo-Kebi. The name Chari-Baguirmi division came from the river Chari. The names of the tributaries of Chari were kept for the district of Logone Oriental and Logone Occidental. The department of Salamat was also named after the tributary of Bahr Salamat that flowed into the Chad Lake.