The word derringer is a widespread misspelling of the surname of Henry Deringer, a famous 19th century manufacturer of small pocket pistols. Other gun manufacturers in various countries made many copies of the original Philadelphia Deringer pistol, with the surname frequently misspelled; this error quickly became a generic word to describe any pocket pistol, along with the generic phrase palm pistol that Deringer's competitors invented and used in their advertising. The original Deringer was a single-shot muzzle-loading pistol; with the advent of cartridge-operated firearms, these pistols began to be produced in their present form, which is still called the derringer.
A derringer is generally the smallest functional pistol of any calibre. They were often used by women, because they were easily concealed in a handbag or as a "stocking pistol".
Derringers are not repeating weapons - repeating mechanisms such as those in a semi-automatic pistol or revolver would make the pistol bulky, defeating its purpose. The original cartridge derringers used only a single cartridge, usually a 10mm caliber, usually spigot or rimfire, with its barrel pivoting to one side of the frame for chamber access and reloading. The design of the famous Remington derringer doubled its ammunition capacity, while retaining its compact size, by adding a second barrel on top of the first.
Today's derringers are used by historical reenactors of the Wild West, as well as concealed carry weapons because of their size and speed of use. Critics do not believe it is a suitable weapon for self-defence, as the derringer has a capacity of two rounds.