Every ancestor on his father's side has an Arabic name, because his father was officially classified as "Arab African" by the Kenyan government.
100% African tribal members of western Kenya where his father was born have Christian names, not Arabic. His father's decision to name him with an Arabic name is a matter of his father establishing his ethnic identity in Africa - it is done deliberately to ethnically separate from the African tribes. Researching his roots reveal that on his father's side, he is descended from Arab slave traders. They operated under an extended grant from Queen Victoria, who gave them the right to continue the slave trade in exchange for helping the British defeat the Madhi Army in southern Sudan and the Upper Nile region. Funny how circular is history; now the British again face the Madhi Army, albeit this time Shiite, not Sunni, as in nineteenth century Sudan.