1550s, from Latin mons Vaticanus, Roman hill on which Papal palace stands. By Klein's sources said to be an Etruscan loan-word and unrelated to vates "soothsayer, prophet, seer" (see vates), but most others seem to think it is related, on the notion of "hill of prophecy" (compare vaticinatio "a foretelling, soothsaying, prophesying," vaticinari "to foretell").