Origin of the Title 'Vatican' According to the Vatican Curator, Ercole Massi

The Vatican Hill takes its name from the Latin word Vaticanus, a vaticiniis ferendis, in allusion to the oracles, or Vaticinia, which were anciently delivered here.

Massi, Ercole G., Compendious Description of the Museums of Ancient Sculpture, Greek and Roman, in the Vatican Palace, 2nd ed., enlarged and improved, Rome: Printing Establishment Morini, 1882, p. 5.