Battle royal

This expression dates from the late 1400s and originates in a military context denoting a battle on a grand scale or of great strength and size. It was soon applied to any contest or confrontation on such scale. Royal is used here as an intensifier, denoting great size, strength or scale rather than a battle involving royalty. Its origin does not come from cockfighting as some suppose, although it may well have been used in this context, where cockerels would engage in “battles royal” to the death.