A promise ring or friendship ring is a small, inexpensive ring given to a boyfriend or girlfriend, to promise not to court a rival. These indicate merely that serious courting is under way. No permanent commitment has been made by either party, but they give the partners an excuse for refusing social invitations from others.
Promise rings have been around for years and years. In the 16th century a promise ring was actually called a gimmal ring and was made up of two to three separate rings with all of the rings coming together the day of a promised wedding.