In case you missed it, in the 1770s, the United States had a revolution, in which it threw out the British King. Since the King was a tyrant who had absolute authority, the new nation of the United States was afraid of giving any one person (or even group of people) too much power.
Democracy comes from the Greek.
Demos means people, specifically every day, ordinary common people.
Cratos mean to rule.
So it means rule by ordinary people. It is a government where power comes from the people.