I can't say for sure but it might be Strychnos pungens or Strychnos
madagascariensis which are found all over southern Africa. I saw them
both in Zambia and Botswana. The colonial name for both is Kaffir
Orange. My understanding is that "Kaffir" is a white Afrikaner
pejorative term for native black Africans which first referred to the
Cape Buffalo (Syncerus cafer) so the common name may not be in common
use due to its offensiveness and political incorrectness.
University of Florida