Brass knuckles
Defined in 2 dictionaries — Ballentine's (1916), Bouvier (1914)
Ballentine's Law Dictionary
James A. Ballentine · 1916
A metal weapon held in the hand and projecting along the back of it. See 22 Tex. App. 679, 3 S. W. 477.
Bouvier's Law Dictionary and Concise Encyclopedia
John Bouvier; revised by Francis Rawle · 1914
A weapon worn on the hand for the purposes of offence or defence, so made that in hitting with the fist considerable damage is inflicted. It is called "brass knuckles" because it was originally made of brass. The term is now used as the name of the weapon without reference to the metal of which it is made; Patterson v. State, 3 Lea (Tenn.) 575.