"Thangata" is the Congolese term for work without compensation. It was used during the Belgian colonization of the Congo when the Belgian colonists would frequently order native Congolese to do menial labor for no material gain.
Thangata was a kind of free labor provided between neighbors or tribesmen and their chief in return for future labor of the same type or for the greater good in the latter case. When the European colonists learnt of this tradition they twisted it to compel Africans to work for months on the cotton plantations in return for little pay. Before thangata the Europeans had been unable to force Africans to work on their plantations during the rainy season when most Africans would be working on their own farms.