In Tuareg hierarchical caste system, the nobles constitute the highest caste. They are known in the Tuareg language as "imúšaɣ" ("Imajaghan", "the proud and free" in the amazigh language). The nobles had a monopoly on carrying arms and camels, were the warriors of the Tuareg regions. They may have achieved their social status by subjugating other Tuareg castes, keeping arms to defend their properties and vassals. They have also collected tribute from their vassals. This warrior nobility has traditionally married within their caste, not to individuals in strata below their own. A collection of tribes, each led by a noble, forms a confederation called "amanokal", whose chieftain is elected from among the nobles by the tribal chiefs. The chietain is the overlord during times of war, and receives tribute and taxes from tribes as a sign of their submission to his authority.