sentences:  They also secured captives as war booty or purchased slaves in markets.The slaves or servile communities are locally called "Ikelan" (or "Iklan", "Eklan"), and slavery was inherited, with the descendants of the slaves known as "irewelen".According to the ethnographer Johannes Nicolaisen (1963), the Ikelan are of assimilated Nilotic origin rather than of Berber heritage like the ethnic Tuareg.