1) Deringer 2) Gun 3) Pistol 1) Handgun 2) Multiple barrel firearm 3) Pistol 4) Pocket pistol 5) Shooting iron 6) Side arm 7) Small gun 
The term derringer is a genericized misspelling of the last name of Henry Deringer, a famous 19th-century maker of small pocket pistols. Many copies of the original Philadelphia Deringer pistol were made by other gun makers worldwide, and the name was often misspelled; this misspelling soon became an alternative generic term for any pocket pistol,...
• (n.) A kind of short-barreled pocket pistol, of very large caliber, often carrying a half-ounce ball.
Small pocket percussion-lock pistol invented by US gunsmith Henry Deringer (1786-1868).
Small pocket percussion-lock pistol invented by US gunsmith Henry Deringer (1786-1868).
Der'rin·ger noun [ From the American inventor.] A kind of short-barreled pocket pistol, of very large caliber, often carrying a half-ounce ball. 
Spelled with two rs, any very small easily concealed handgun.
[n] - a pocket pistol of large caliber with a short barrel
noun a pocket pistol of large caliber with a short barrel
an early short-barreled pocket pistol.