Both rich and poor Roman parents hung a bulla around their newborn child's neck to protect him or her from misfortune or injury. A bulla could be as simple as a knotted string of cheap leather or as elaborate as a finely made chain necklace holding a golden locket containing a charm thought to have protective qualities. Girls wore their bullas until their wedding day and boys wore theirs until they became citizens (full members of society) at age sixteen. Some men, such as generals, would wear their bullas at ceremonies to protect them from the jealousy of others. Although bullae (plural of bulla) had spiritual and legal significance, during Roman times, the Etruscans, from modern-day central Italy, wore embossed bullae in groups of three as purely decorative ornaments for necklaces and bracelets or, for men, as symbols of military victories.
Payne, Blanche, Geitel Winakor, and Jane Farrell-Beck. The History of Costume: From Ancient Mesopotamia Through the Twentieth Century. 2nd ed. New York: HarperCollins, 1992.