The magnitude scale dates to before the ancient Roman astronomer Claudius Ptolemy, whose star catalog popularized the system by listing stars from 1st magnitude (brightest) to 6th magnitude (dimmest). The modern scale was mathematically defined in a way to closely match this historical system.
If you could see the earth illuminated when you were in a place as dark as night, it would look to you more splendid than the moon. Galileo Galilei, Salviati, p. 88