(slang, offensive) a Jew 1922: Shylock chimes with the jewbaiting that followed the hanging and quartering of the queen�s leech Lopez, his jew�s heart being plucked forth while the sheeny was yet alive � James Joyce, Ulysses
http://en.wiktionary.org/wiki/sheeny
Offensive Slang Used as a disparaging term for a Jew.
http://www.bartleby.com/61/87/S0328700.html
http://www.infoplease.com/dictionary/sheeny
kike, hymie, sheeny, *** -- ((ethnic slur) offensive term for a Jew)
http://poets.notredame.ac.jp/cgi-bin/wn?cmd=wn &word=sheeny
Llittle jingle, which means that "sheeny" survives somewhere as acceptable conversational vocabulary, which is depressing, to put it mildly. "Sheeny" is a very old and extremely derogatory term for a Jewish person. It first appeared in the 19th century and its origin is uncertain, but it may be based on the German word "schon," meaning "beautiful." The theory is that Yiddish-speaking Jewish merchants pronounced "schon" as "sheen" when advertising their wares, and the word was then picked up as slang for Jews in general. While "sheeny" was at first not especially negative in connotation (and was used by Jews themselves in a joking sense in the mid-19th century), in the 20th century it has become an unambiguously anti-Semitic slur, on a par with "kike."
http://www.word-detective.com/back-y.html#shee ny