http://pages.ucsd.edu/~dkjordan/resourc ... nsion.html
"Between 2500–3000 years ago, speakers of the original proto-Bantu language group began a millennia-long series of migrations eastward from their original homeland in the general Nigeria and Cameroon area of West Africa. This Bantu expansion first introduced Bantu peoples to central, southern and eastern Africa, regions where they had previously been absent from.
Some Bantus in Somalia are believed to be direct descendants of these early migrants from West Africa. Most, however, are descended from Bantu groups that had settled in Southeast Africa after the initial expansion from Nigeria/Cameroon, and whose members were later captured and sold into the Arab slave trade."
Most maps of the Bantu expansion do not show it entering Somalia. If it did, it would have come from Uganda and been the tip of a spear that then turned south.