This is seriously the greatest discovery OF MY LIFE. AHAHAHAHAHAHAHA.
Dictionary.com agrees: "1914, Amer. Eng., from hobo slang, "a catamite;" specifically "a young male kept as a sexual companion, esp. by an older tramp," from Yiddish genzel, from Ger. Gänslein "gosling, young goose." The secondary, non-sexual meaning "young hoodlum" seems to be entirely traceable to Dashiell Hammett, who snuck it into "The Maltese Falcon" (1939) while warring with his editor over the book's racy language."
And so does even the OED! (Concise OED, 11th ed) "gunsel: noun / United States / informal a criminal carrying a gun. Origin: early 20th cent. (denoting a tramp's young companion): from Yiddish gendzel 'little goose', influenced by gun."
OH OED! Your euphemizing does you more (hilarious) harm than good!