The Romans were the first to coin the term Battle Royal, using it to describe a specific type of spectacle in which several gladiators were matched in one arena and made to fight until only one remained.
It was not until a resurgence in boxing in 19th century America that battle royals once again became commonplace attractions, specifically using black fighters. These events often took place as preludes to larger, more legitimate fights and were conducted in "smokers"--illegally staged and unregulated boxing "shows" secretly held in remote locations.
Typically the winner of a battle royal would collect a meager purse of coins tossed to him by the spectators at the fight's conclusion.
Many of the most famous black fighters of the 19th and early 20th century participated in battle royals.
Source for much of this: Invisible Ring: The Role of Prizefighting and the Battle Royal in Invisible Man .