 The "Hassan" monopolized the occupations related to war and politics, the "Zwaya" (Zawaya) the religious roles, the "Bidan" (White Moors) owned property and held slaves (Haratins, Black Moors), and the slaves constituted the lowest of the social strata.Each of these were castes, endogamous, with hereditary occupations and where the upper strata collected tribute ("horma") from the lower strata of Mauritanian society, considered them socially inferior, and denied them the right to own land or weapons thereby creating a socio-economically closed system.Among Hassaniya Arabic speakers in southern Morocco and Mauritania, states Sean Hanretta – a professor of African History, the term "Bidan" is a "caste synecdoche" that refers to "Hassani" (warrior) and "Zwaya" (clerical) clans.