La Bulla

1. a bubble
2. a swollen or bubble-shaped object, particularly:

• a knob, boss, or stud, as on doors, shields, etc.
• (historical) a bulla: a protective (usually golden) amulet worn by upper-class Roman children
• (Medieval Latin, historical) a round metallic seal certifying official medieval documents, particularly the golden imperial seal and the leaden papal one.

3. (Medieval Latin) a papal bull or other official document sealed with a bulla