Swahili is a hugely popular language in Africa, spoken by over 50 million people. The initial spread of the language across Africa is owed to the traders from the Arab region that carried the language as far west as Congo and North to Uganda.
Later when the Germans colonized parts of Africa, they chose to use Swahili as the administrative language. The Tanganyika and the English standardized the language and helped create the Latin based script it still uses today.
Swahili, because of its scale and presence in the continent, is often the default language used by African-Americans to show their connection to their roots and the motherland.