Green’s Dictionary of Slang

a Jew whose family come from Lithuania and are therefore considered lower-class by Jews from Poland; also attrib.

1928		A. Burstein Ghetto Messenger 176: He’s a Litvak! I don’t want him!
1939		J. Weidman What’s In It For Me? 76: Litvaks, they fry in oil. But regular people, [...] its butter.
1942		N. Algren Never Come Morning (1988) 7: Was not Greek, was Litvok.
1951		(con. 1910s) S. Longstreet Pedlocks (1971) 228: It could have been worse. He might have been a Glitz or a Litvak.
1975		L. Rosten Dear ‘Herm’ 7: It is of Litvak derivation.