Kike is derogatory term for someone who is Jewish. Early evidence suggests it was used at first among German-American Jews in reference to newcomers from Eastern Europe, perhaps because the names of the latter ended in -ki or -ky."
Another theory "suggests a source in Yiddish kikel "circle." Accordingly, Jewish immigrants, ignorant of writing with the Latin alphabet, signed their entry forms with a circle, eschewing the customary "X" as a sign of Christianity. On this theory, Ellis Island immigration inspectors began calling such people kikels, and the term shortened as it passed into general use."
- Online Etymology Dictionary
- The Words "Kike" and "Anti-Semite" Were Both Coined by Racist Jews, Who Hated Other Jews by Christopher Jon Bjerknes