c. 1300, revelacioun, "disclosure of information or knowledge to man by a divine or supernatural agency," from Old French revelacion and directly from Latin revelationem (nominative revelatio), noun of action from past-participle stem of revelare "unveil, uncover, lay bare" (see reveal).
The general meaning "disclosure of facts to those previously unaware of them" is attested from late 14c.; meaning "striking disclosure" is from 1862. As the name of the last book of the New Testament (Revelation of St. John), it is attested from late 14c. (see apocalypse); as simply Revelations, it is recorded by 1690s.