mystery: [14] Greek múein meant ‘close one’s eyes or mouth’, and hence was used figuratively for ‘keep secret’. Its association with secret initiation ceremonies inspired the formation from it of muein ‘initiate’, whose derivative mústēs meant ‘initiated person’. This in turn formed the basis of mustérion ‘secret ceremony, secret thing’, which passed into English via Latin mystērium. Also derived from mústēs was mustikós, from which ultimately English gets mystic [14] and mystical [15]. => mystic
