Interestingly, the pejorative
"kike" was first applied to the Russian Jews who immigrated
to New York City
in the mid 1880s by the German-descended Jews who were already there.
During the decade of the 1880s over 200,000 Eastern European Jews arrived in the United States, and around 140,000 of them decided to stay in New York City. Until the late 1870s and early 1880s the vast majority of the Jewish population of New York City were immigrants, or descendants of immigrants, from Germany.
Western European Judaism had diverged considerably from Eastern European Judaism over the centuries, with the Western "style" conforming much more closely to the social norms of the Christian society around it. German Jews carried their culture with them across the Atlantic and, as such, the inital character of New York City Judaism was that of Western Europe.
When Eastern European Jews began arriving in New York the established Jewish community was largely made uncomfortable. The new arrivals were (for the most part) peasants, while the German Jews in New York occupied a middle and (occasionally) upper class. So there was immediately a class divide to deal with, and in an extremely class-stratified city there was little effort to unite across class lines. Indeed, German Jews saw the newbies as a great pool of cheap labor for the garment industry, which they completely dominated.
Additionally, New York's German Jews were attempting to distance themselves from a group which quickly became yet another target of anti-immigrant racism on the part of the "native" New Yorkers. German Jews were themselves beginning to be victimized by growing anti-Semitism, and as a defense mechanism tried to illustrate and publicize how they differed from the "miserable darkened Hebrews" (in the words of the Hebrew Standard newspaper), that "standing menace" whose "loud ways and awkward gesticulations are naturally repulsive and repugnant to the refined American sensibilities" (or so said the Rev. Dr. J. Silverman, speaking at Temple Emanu-El in 1889).
"Kike" was developed by the German Jews as a catch-all term of disdain for Eastern European Jews because, supposedly, of the prominence of the syllable "ki" which ended many of the Easterners' surnames.
Solidarity between Western and Eastern European Jews in the United States would take many decades to develop.
data and quotations lifted from Gotham: A History of New York City to 1898 by Edwin G. Burrows and Mike Wallace (no relation).