There were a number of Kimbundu dialects and groups. Two, each incorporating Portuguese terms, gradually became dominant, serving as lingua francas for many Mbundu. The western dialect was centered in Luanda, to which many Mbundu had migrated over the years. The people speaking it, largely urban, had come to call themselves Ambundu or Akwaluanda, thus distinguishing themselves from rural Mbundu. The eastern dialect, known as Ambakista, had its origins in the eighteenth century in a mixed Portuguese-Mbundu trading center at Ambaca near the western edge of the plateau region, but it spread in the nineteenth century through much of eastern Mbundu territory. Another Kimbundu-speaking group, the Dembos, were generally included in the Mbundu category. Living north of Luanda, they had also been strongly influenced by Kikongo speakers.