The word dates back to the late 19th century. Origin is debateable. May theories exist, the most plausible in my opinion is as follows: To borrow from Leo Rosten’s The Joys of Yiddish, ‘The word kike was born on Ellis Island, when Jewish immigrants who were illiterate (or could not use Roman-English letters), when asked to sign the entry-forms with the customary ‘X,’ refused — and instead made a circle. The Yiddish word for ‘circle’ is kikel (pronounced KY – kel), and for ‘little circle,’ kikeleh. Before long the immigration inspectors were calling anyone who signed with an ‘O’ instead of an ‘X’ a kikel or kikeleh or kikee or, finally and succinctly, kike.’ Rosten explains that for the Jewish immigrants, an ‘X’ was an evil sign, representing both the horrors of crucifixion and the sign of their (Christian) oppressors. Jewish – American merchants continued to sign with an ‘O’ instead of an ‘X’ for several decades, spreading the nickname kike wherever they went as a natural result. At that time kike was more of an affectionate term, or used by Jews to describe other Jews, and only developed into a racial slur later on.