We need to talk about 'Kike' -- how did the slur originate anyway?

Everyone knows what the word “kike” means, but not everyone agrees on where the word comes from. That mystery is back in the headlines with yet another viral use of the slur — this time, it was NBA player Meyers Leonard who unleashed the word during a heated gaming moment.

“Dictionaries prefer to say that its origin is unknown, which is right but uninspiring,” Anatoly Liberman wrote on the Oxford English Dictionary blog in 2009, as part of a series he did on ethnic slurs.

And to make matters more complex, the OED was unable to officially identify any uses of “kike” before 1904. That means we move to the world of theories.

One intriguing theory is that “kike” comes from Yiddish. In the “Joys of Yiddish,” Leo Rosten notes that the word kike “was born on Ellis Island when there were Jewish migrants who were also illiterate (or could not use Latin alphabet letters. When asked to sign the entry-forms with the customary “X”, the Jewish immigrants would refuse, because they associated an X with the cross of Christianity.”

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I have always been fascinated by etymology and the first theory floated about "kike" is the one with which I am most familiar. I have studied a variety of different words and their histories and in the last couple of years have read some really good books about word origins. Personally, I have always been interested in the origins of slurs. Many are easy to track down, others, like the one this article is about, not so much. When I was in college, I even tried to hunt down the origin of the word "dyke" as the reference made to lesbians to no avail.

In the above article, had you heard of any of the alternate theories? What are some words you have wondered about or tried to hunt down its meaning?