Kafir is what the Koran and Islam call the unbelievers.
It is an inflection of the verb
kafara, which means "to conceal,' and from that came to mean "to deny." So a
kaffir (the standard spelling in English) is one who
denies the alleged truth of Mohammed's teachings.
Originally the word was applied to all non-Muslims, but during the Ottoman era it was narrowed to mean only Christians, if the context of the discourse did not suggest otherwise.
But the Christian missionaries in Africa borrowed it in its original sense, which is an almost perfect translation of our word "heathen." They applied it to the Bantus, and by extension it came to mean any of the native peoples of South Africa. From there it developed in almost the same way as the Spanish word
negro (meaning simply "black person" with no judgment implied) developed in the USA, as Southern dialect changed the pronunciation to "nigger" and made it an ethnic slur. By the early 20th century "Kaffir" was regarded as an ethnic slur and in post-apartheid South Africa it is now understood to have
only that meaning.
In South Africa today it is not just oafish but
illegal to call someone a kaffir, and people can be arrested for it. This makes it much worse than our N-word.
* * * * Hey I'm only going to spell the whole word out once in a month. I don't want to trigger all the filters that will block this website from corporate, educational and family computers. So don't think it would be cute to repeat it twelve times. I'll edit your posts immediately! I don't really expect that to happen because you folks who post on the Linguistics board are much more mature and sensible than some of our other members.

* * * *
Kafir is the worst word in the human language.
The South Africans certainly agree with you. But it's not because it means "infidel." It's because it's an ethnic slur that developed from a religious slur!
In any case, every culture has "fightin' words" as we say in English: words so inflammatory that they are guaranteed to start a fight. In fact they are one of the very few exceptions to our constitutional tolerance for free speech, in the same category as fraud, libel, copyright violation, incitement to riot, conspiracy to commit a crime, and advocacy of overthrowing the U.S. government by force.
And they change with the generations. Afro-Americans beat us over the head with the N-word in their rap songs and laugh about it because our laws always lag one generation behind culture so if we use it we might be prosecuted. Asian-Americans were using rude English slang words for their people when I first moved to Los Angeles fifty years ago, and today if you say "Buddha-head" most people will have no idea what or whom you're talking about. Does anybody even remember "wop" for an Italian and "mick" for an Irishman?' My parents would never have dared to utter those words in mixed company when they were growing up in Chicago in the 1910s. "Frog" for a Frenchman and "kraut" for a German are now acceptable as humor and there's even a style of music called "kraut-rock."
So "kaffir" will surely become passe during this century.
If Kafir means non believer then I am proud to be Kafir.
Nonetheless it behooves all of us to not go around casually making people uncomfortable with our choice of words. There are millions of moderate Muslims in the USA who A) don't use that word and B) don't believe that non-Muslims are bad people but C) are not quite as assimilated and cosmopolitan as our grandparents were. If you call yourself (or anyone) a "kaffir" in their presence you'll just embarrass them and make them squirm. Why do that?
It's just about exactly the same as learning another language's profanity before you learn how to speak the language, or even before you learn much of anything else about the culture. It's an insult.
How would you feel about a person from Ghana or Tanzania who just arrived in America and can't speak a word of English, except he goes around spouting the words "bullshit," "asshole," "motherfucker"... and the N-word?
That's exactly the way those moderate Muslims will feel about you if you tell them, "I'm proud to be a kaffir."
Be nice to people. It will make them feel good and it will also make you feel good.
