What is the origin of the idiom "love child" and when to use it?

The idiom "love child" is thought to have originated in the 17th century. It is believed to be a reference to the fact that children born out of wedlock were often considered to be the result of a romantic relationship between two people who were not married. The term "love child" is often used in a negative or disapproving way, as it implies that the child is the result of a casual or illicit relationship. However, it is also sometimes used in a more neutral or positive way, as a way to describe a child who was born into a loving and supportive relationship.