BULLA. – A lentil-shaped, hollow capsule formed of two overlapping plates and provided with a loop for wearing around the neck. Sometimes it took the form of a heart or a crescent. It was in general use among the Etruscans, who attributed prophylactic virtues to II. The Romans adopted it from them, and among the Romans it was worn by freeborn boys and girls, both male and female, as those most exposed to the influences of the evil eye and spells. It was made of metal, often precious, for the sons of patrician senators and knights, and of leather for others. It usually contained objects possessing special prophylactic virtues. It was deposited and offered to the household gods at the age of seventeen, when boys assumed the toga of manhood, and at about the same age by girls when they married. The faces of the bulla were ordinarily smooth, but those made of metal were sometimes adorned with embossed reliefs, usually busts of children or deities.
Among Christians in the early centuries, the use of bullae continued, more out of custom than superstition. They sometimes adorned the front face with Christian representations, especially the Christological monogram. It seems that they often placed inside them relics of holy martyrs, thus making them into true reliquaries, or even small sheets of parchment with invocations and exorcisms against the powers of darkness.