The Vatican Secret Archives (Latin: Archivum Secretum Vaticanum), located in Vatican City, is the central repository for all of the acts promulgated by the Holy See. These archives also contain the state papers, correspondence, papal account books, and many other documents which the church has accumulated over the centuries. In the 17th century, under the orders of Pope Paul V, the Secret Archives were separated from the Vatican Library, where scholars had some very limited access to them, and remained absolutely closed to outsiders until 1881, when Pope Leo XIII opened them to researchers, of whom now more than a thousand examine its documents each year.
The word “secret” in the title “Vatican Secret Archives” does not have the modern meaning: it indicates instead that the archives are the Pope’s own, not those of a department of the Roman Curia. The word “secret” was used in this sense also in phrases such as “secret servants”, “secret cupbearer”, “secret carver”.
I bet there are a lot of secrets here.