What is "ruga-ruga"

Ruga-Ruga (sometimes called Rugaruga) were irregular troops in Eastern Africa, often deployed by western colonial forces. They often served as mercenaries or local auxiliaries alongside the regular Askari, professional soldiers who were often hired in other regions of Africa. While the latter were trained by officers of the European colonial powers in Africa, the Ruga-Ruga were mostly hired from tribal warriors during times of conflict.