Great King, eh? How imaginative! It actually means dysmenorrhoea caused by an intestinal parasite.
Reason was, his mother fell pregnant as a result of an affair with the then king of the Zulu, and had to leave in disgrace; when the cause of her lack of menstruation was born, his nickname became Shaka = the parasite aforesaid.
I do hope this has got nothing to do with Chaka! (If it was French, I'd expect the same sound in both halves, like Fifi or Chouchou. But my French is sadly limited ...)