An over-reaching dealer, or hard, sharp fellow; an extortioner: the brokers formerly behind St. Clement’s church in the Strand were called Jews by their brethren the taylors.
Definition taken from The 1811 Dictionary of the Vulgar Tongue, originally by Francis Grose.
See also the definition in Nathan Bailey's 1736 dictionary of canting and thieving slang.
Jet * Jew-1Nathan Bailey's 1736 Dictionary of canting and thieving slang
John S. Farmer's collection of canting songs and slang rhymes