Populus means "people" or "population". It's a very common root that appears in many English words, including:
* Popular: Meaning "of the people" or "liked by many people".
* Populate: Meaning "to fill a place with people".
* Population: Meaning "the number of people living in a particular place".
* Republic: Meaning "a state where supreme power is held by the people".
* Public: Meaning "relating to the people as a whole".
So, the root "populus" essentially carries the meaning of "the people" and is used to form various words related to the concept of people and their collective identity.