Every papal bull has always been known by the first few words with which the text of the bull began. For example, Pope Innocent II’s bull of 1139 which officially approved the Knights Templar has always been known as the ‘Omne datum optimum‘ bull, on account of the bull’s opening words ‘every perfect gift’.
The practice of titling and designating a written work based on its opening words was not confined to the papal curia and may not even have originated there. Many medieval libraries developed a system of listing their books by their opening words. It was a brilliant idea. In a book culture where not every written work carried a title, the opening words were a good indexing trick. It allowed the librarian to quickly identify which book is which and to make sure that the library catalogues are up to date. It was also a way of raising the profile of an untitled book by
The Middle Ages were a formative period for our current book cultures, and most of the features of the modern book were developed in the medieval period. And while we expect every book to have a title (how on earth would we refer to it otherwise?), the truth is that most books produced in the Middle Ages didn’t have a title. In the field of history writing, most chronicles and annals produced in the thousand years between the fall of Rome and the Renaissance are known to us based on names and titles bestowed on them by modern scholars. The famous Anglo-Saxon Chronicle was never known in its time by this name. Another chronicle whose study took 4 years of my life is now known as the “Crowland Chronicle”, the name I gave it and under which it had never circulated in medieval England.