What is "fenya"

n. A Russian cant language used among criminals.

Fenya (феня) or fenka (фенка) is a Russian cant language used among criminals. Originally it was a cryptolanguage of ofenyas or ofenes, old Russian peddlers, and had a number of names or it might come from the Russian word фен or fen which is the west wind. There are no convincing explanations about the origins of the words "ofenya" and "fenya". In modern Russian language it is also referred to as blatnoy language (Russian: блатной язык), where "blatnoy" is a slang expression for "criminal". It is also widely used in "thieves' songs".