Angelo was born Domenico Demetrio Calogerà circa September 7, 1696, in Padua, Republic of Venice, to Don Liberale Calogerà of Corfu and Giustina Labarvellon. His father was a member of the aristocratic House of Calogerà and had distinguished himself in the War of Cyprus against the Ottoman Empire in the 1570s; eventually, he settled in Padua, held several administrative posts there, and finally moved to Venice and gained Venetian citizenship. In 1716 Angelo became a Camaldolese monk, initially as librarian of the San Michele di Murano and later as prior of San Giorgio Maggiore.