The idea of the wedding ring as a symbol of love is relatively modern. The ring was originally regarded as both a down payment on the bride and a sign to other men that she was no longer available. It was, in effect, a 'property sold' sign. Even the word 'wed' comes from the Anglo-Saxon term for a security given in order to bind a promise.
The ancient Hindus were among the first to use wedding rings, and the tradition was exported to the West by the Greeks and Romans. The ring remained a 'property sold' sign until the 9th century, when the Christian Church adopted it as a symbol of fidelity.
It is hardly surprising that to lose, break or remove such a powerful symbol was thought to have dire consequences. In parts of Scotland there is a belief that if a woman loses her ring she will also lose her man. If the ring is dropped at the wedding ceremony and it rolls away from the altar, this is a terrible omen. And if the ring ends up on a gravestone, one of the newlyweds faces an early death - the victim is determined by the sex of the person buried in the grave.
The choice of the ring finger is also connected with various myths. The fourth finger of the left hand was chosen by the ancient Greeks and Romans as they mistakenly believed that a vein ran directly from it to the heart. That a woman's ring is generally, but by no means universally, worn on the left hand, stems from the belief that this was the weak hand, symbolising woman's submission to man.