German Kaffer via Yiddish from Hebrew kfar = village: silly or stupid peasant. Arab. kâfir: infidel, unbeliever. In Arabic there is also kafr = village from the same root KFR.
In South Africa during the Apartheid regime kaffer was the derogatory term for official Bantu: Negro.

The change from Kanaka to germ. Kanake is in assimilation to the determined form of the adjective; sometimes, in dialect, you may also hear the indetermined form Kanaker.

I must confess that I sometimes use the term Kanake when working between the shelves and swearing at the students unable to put back the books in the right order. Here in the sense of definition 2 given by MudGuard. It may be substituted by Bimbo.

Wilfried