American socialites used to be listed in the Social Register. It was a list of names and addresses of the people who were thought to be more socially acceptable in the socially important families in the 19th century. In 1886, Louis Keller had the idea of combining these lists and selling them. Mr. Keller had great success. By 1918 there were 18 yearly volumes that covered 26 cities.
The term includes many people who are "famous because they are famous". These people are not famous because of something they have done. They are famous most often because of which family they are a member of and/or how they are talked about by the media.