The Numayrid emirs (princes) belonged to the Banu Numayr tribe, the dynasty's namesake. The Banu Numayr were a branch of the Banu 'Amir ibn Sa'sa' tribe and therefore of Qaysi, or north Arabian, lineage; the Arab tribes were roughly divided into northern and southern Arabian lineages. The name Numayr is likely associated with nimr, the Arabic word for leopard. Unlike most of the children of 'Amir ibn Sa'sa' who became progenitors of large branches of the tribe, Numayr was thought to have had a different maternal lineage and did not enter into any tribal alliances. For much of their history, the Banu Numayr were an impoverished, nomadic group that mostly engaged in brigandage. They did not enter the historical record until the Umayyad era (668-750 CE) when they dominated the western hills of al-Yamamah in central Arabia. As a consequence of their brigandage, the Banu Numayr were dispersed in an expedition by the Abbasid general Bugha al-Kabir in 846, but recuperated in later decades.