"Kaffir" is an Islamic word that means infidel. It was widely used as a racial slur against black people in 19th and 20th century South Africa, and probably originated among the Cape Malay people, who are Muslim. As Mathabane points out in a note preceding the text, it is equivalent to the n-word used in the U.S. as a racial slur for black American. Mathabane's use of the term here is ironic. He does not think he is a "kaffir" in the manner the term implies. Rather, it is an attempt to reclaim the word, in much the same way the gay community has reclaimed the word "queer," wearing the label proudly rather than allowing it to provoke shame.