Dominum Deum Nostrum Papam

The origins of the phrase "Dominum Deum Nostrum Papam" are found in the Extravagantes of Pope John XXII which were a collection of twenty papal constitutions issued during his pontificate (1316–1334) that circulated outside the established collections of the Corpus Juris Canonici. Because these decretals were “wandering outside” (extra vagantes) the earlier canonical collections, they came to be known as the Extravagantes. In 1325, the canonist Zenzelinus de Cassanis (also called Zenzelino de’ Cassani) gathered the twenty constitutions into a systematic collection and supplied them with a detailed gloss, or legal commentary.  It was in his commentary on chapter 47 Quia quorundam mentes where we find the statement "Dominum Deum Nostrum Papam".   

The Extravagantes and their accompanying gloss were authoritative because they formed part of the developing body of papal canon law used by medieval canonists and ecclesiastical courts. The Extravagantes collected papal decretals that circulated outside the earlier canonical collections, while the gloss provided the interpretive commentary of recognized canonists, explaining how the decretals were to be understood and applied. Together, the decretals and their glosses became standard materials in the teaching and interpretation of canon law and therefore carried substantial weight in determining accepted ecclesiastical doctrine and legal practice.   The later Correctores approved the Roman edition of the Extravagantes in 1582 and 1584, and the edition retained the reading “Dominum Deum nostrum Papam” (“our Lord God the Pope”), preserving the controversial wording found in the original 14th century Vatican source in the officially corrected roman text of the 16th century.  In addition, the gloss itself was consistent with the main body of canon law (Distinctio 96, Chapter "Satis Evideter") which also shewed the pope could justly be called god.   

Over the years, some catholic blogs and even a jesuit have outright claimed the original vat.lat.1397 did not have the gloss, suggesting perhaps it was only a later scribal interpolation.   While several editions published over the years did omit the word deum from the text, the original vat.lat.1397 did in fact retain the gloss as well as the roman approved and corrected edition.   This was further commented upon by António Pereira de Figueiredo (1725–1797), who was a Portuguese Catholic theologian, priest, and biblical scholar who became an important Jansenist-leaning critic of ultramontane papal authority.  He noted that the pope had never denied usage of the title.   While some Catholic blogs have questioned his existence, his work "Tentative Theologica" is publicly available online.