A more thorough explanation:

Filius populi is a Latin term that means "son of the people" or "son of nobody." In history, it referred to an illegitimate child who had no legal father.

According to William Blackstone's Commentaries on the Laws of England, a bastard or illegitimate child was considered a filius nullius or filius populi. This meant that they had very few rights and could not inherit anything from their father.

For example, if a woman had a child out of wedlock, the child would be considered a filius populi and would not have any legal claim to their father's property or inheritance.

The term filius populi was used to describe an illegitimate child who had no legal father. This meant that they had very few rights and could not inherit anything from their father. The example of a child born out of wedlock illustrates how the term was used in history.