Papal bull
A papal bull is a particular type of letters patent or charter issued by a Pope of the Catholic Church. It is named after the lead seal (bulla) that was appended to the end in order to authenticate it.
History
Papal bulls have been in use at least since the 6th century, but the term was not used until around the end of the 13th century, and then only internally for unofficial administrative purposes. However, it had become official by the 15th century, when one of the offices of the Papal chancery was named the "register of bulls" (registrum bullarum).
By the accession of Leo IX in 1048, there develops a clear distinction between two classes of bulls of greater and less solemnity. The majority of the "great bulls" now in existence are in the nature of confirmations of property or charters of protection accorded to monasteries and religious institutions. At an epoch when there was much fabrication of such documents, those who procured bulls from Rome wished to secure that the authenticity of their bulls should be above suspicion. A papal confirmation, under certain conditions, could be pleaded as itself constituting sufficient evidence of title in cases where the original deed had been lost or destroyed.