mystery [ME] Mystery goes back to Greek mustērion, which is related to mystic [ME] and mystify [E19th]. In ancient Greece mysteries were secret religious ceremonies witnessed only by the initiated, who were sworn never to disclose their nature. In Christianity the word means either a truth long kept secret but now revealed through Christ, or something of symbolic significance. The first English uses of mystery were in religious contexts, but it soon spread into wider use for something inexplicable or beyond human comprehension [LME], and then for simply a puzzle or conundrum. In the heyday of British coach parties the mystery tour [1920s] to an unspecified destination was popular.