(Arabic, Kâfir. an infidel). A name given to the Hottentots, who
reject the Moslem faith. Kafiristan, in Central Asia, means “the
country of the infidels.” “The affinity of the Kafir tribes ...
including the Kafirs proper and the people of Congo, is based
upon the various idioms spoken by them, the direct
representatives of a common, but now extinct, mother tongue.
This aggregate of languages is now conveniently known as ... the
Bantu linguistic system.” — Source: Dictionary of Phrase and
Fable, E. Cobham Brewer, 1894 More on Kaffir from Infoplease: