In many states, the aristocracy included the upper class of people (aristocrats) with hereditary rank and titles.
The term aristokratia was first used in Athens with reference to young citizens (the men of the ruling class) who led armies at the front line.
Due to martial bravery being highly regarded as a virtue in ancient Greece, it was assumed that the armies were being led by "the best".
From the ancient Greeks, the term passed to the European Middle Ages for a similar hereditary class of military leaders, often referred to as the nobility.
As in Greece, this was a class of privileged men and women whose familial connections to the regional armies allowed them to present themselves as the most "noble" or "best" of society.