The Motu proprio notes that the Vatican’s archives were founded at the beginning of the 17th Century. The Church collected and stored important documents and writings from both religious and secular spheres of life. In the early years the archives were not open for scholars to visit, rather copies of documents produced by Vatican workers were sent around the world to scholars who requested them. For this reason, the Pope says, the philosopher and mathematician Gottfried Wilhelm von Leibniz referred to the Archive as the “Central Archive of Europe.” The archives were opened to visiting scholars in 1881.
Pope Francis explained his reasons for changing the name of the archive by pointing out the meaning of the word “secret” or “secretum” in Latin, which is still the official language of the Catholic Church. Secret was usually translated to mean “private.”
“As long as there was still an awareness of the close link between the Latin language and the languages that derive from it,” the Pope said, “there was no need to explain or even justify this title of Archivum Secretum.” As languages developed however, the word “secret” began to take on a more negative meaning, used for knowledge or information which needed to be withheld from the general public, for fear of a scandal.
“This is entirely the opposite of what the Vatican Secret Archive has always been and intends to be” wrote the Pope, explaining the change.
Source: Vatican News