From: Ga, West Africa
Source: Ga (Ghana) proverb; Joshua N. Kudadjie, "Ga and Dangme Proverbs for Preaching and Teaching" (Asempa Publishers, 1996; read in the afriprov.tangaza.ac.ke edition), which adds: "Turning your buttocks on another is a sign of contempt."
The source explains it: expresses the conviction that gratitude is proper and must be sincere
. The wording of the meaning is ours.