An Etymological Dictionary of the German Language/Gauner

by Friedrich Kluge

Gauner, earlier Jauner, m., ‘sharper, knave,’ does not occur till the beginning of the last century; in the 15th and 16th cents. the professional swindlers at cards were called Joner, from the slang jonen, ‘to play,’ the ultimate source of which is said to be Hebr. jânâ, ‘to cheat.’