The Collaborative International Dictionary of English v.0.48:

goniff \gon"iff\, n. [From Yiddish, prob. fr. Heb. gann[=a]bh
   thief.]
   A pickpocket or thief. [Also spelled ganef, gonif, and
   gonoph.] [Eng. Slang]
   [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

Gonoph \Gon"oph\, n. [From Yiddish, prob. fr. Heb. gann[=a]bh
   thief.]
   A pickpocket or thief. [Also spelled ganef, gonif, and
   goniff.] [Eng. Slang] --Dickens.
   [1913 Webster]