In the Vatican, the "holy" language is Latin. In the ancient Roman religion of (the pagan) Pantheon temple, the language was Latin.
The word "Catholic" means "universal." Likewise, the word "pan" means "universal" or "all-inclusive." The word "pantheon" is a compound word comprised of the word "pan" and "theon," which is a form of "theos." Theos means "god." Together, the words refer to the worship of "all god(s)."
The word "cardinal" is from the word "cardin" and "cardo," which refer to a "hinge." The priests asociated with Janus, the Latin god of the door, were sometimes called "cardinals." Today, a select group of Latin high priests commissioned by the Vatican are called "cardinals."
The pagans of ancient Rome (and elsewhere) recognized their gods as "patron" gods with jurisdictions over particular localities and powers over certain elements. Temples, altars, shrines, and statues to patron gods were used in ancient Rome and elsewhere. The Vatican has "patron" saints with their own temples, altars, shrines, and statues.
And lastly, the high priest of the ancient pagan Etruscan and later Latin priesthood was known as the "Pontifex Maximus" (or Supreme Pontiff). The high priest in the Vatican today is called the (Sumpreme) Pontiff.
The ancient Latin people dedicated days and months to their gods and the gods they adopted from other people. The current western calendar, which is a form of the Roman Catholic Church's Gregorian Calendar still contains the names of pagan gods on it. Why would a Christian, which is what Gregory said to have been, place pagan deities on a "Christian" calendar? Was he attracting pagans with this move, or continuing to show that the Latin Church was a continuation of the ancient religions they claimed to be replacing?
Those seeking to understand the significance of the word "vatican" and/or its connection to Christianity or pre-Christian religion should consider the names associated with the Vatican along with the symbols and practices of the religion whose capital is Vatican City, the City of Seven Hills.