apocalypse

From Middle English apocalips, from Latin apocalypsis, from Ancient Greek ἀποκάλυψις (apokálupsis, "revelation"), literally "uncovering," from ἀποκαλύπτω (apokalúptō, "to reveal"), itself from ἀπό (apó, "away from") plus καλύπτω (kalúptō, "to cover") and the noun-forming suffix -σις (-sis).

The word originally meant simply a revelation or uncovering of hidden things. It came to mean catastrophe or the end of the world through its association with the biblical Book of Revelation, also known as the Apocalypse of John.

The verb form comes from the noun, and in its 'reveal' sense is a semantic loan from the same Greek verb, ἀποκαλύπτω, that gave us the noun in the first place.