The term GUN, IN SLANG can be broken down into three crossword solutions: ROD (3 letters), GAT (3 letters) and PIECE (5 letters). ROD is a slang term for a gun that originated in the early 20th century, likely derived from the phrase 'ROD of iron'. GAT is a slang term for a gun that originated in the 1920s, likely derived from Gatling gun. PIECE is a slang term for a gun that originated in the late 19th century, likely derived from the phrase 'PIECE of iron'. All three terms are still used today to refer to a gun.