The word for today is MYSTERY. The various religions of the world have mysteries. A mystery is something that is not fully understood or that baffles or eludes understanding. A religious cult practices secret rites to which only initiates are admitted. When the cult of the Egyptian goddess, ISIS, came into the ROMAN mainland it attracted many followers. Other far Eastern religions also worked their way into the ROMAN world. Each religion demanded secrecy from its adherents. In fact, the new converts to Christianity would not be allowed up front during the ceremony. They were relegated to the back where they barely could hear the celebrant.
The late Latin word – MYSTERIUM – means – A SECRET RITE. Originally it came from the Greek word – MUSTES – which means – AN INITIATE. This came from the Greek verb – MUEIN – meaning – TO CLOSE THE EYES. This definition, of course, needs no explanation.
The Roman Church refers to 15 incidents in the life of JESUS & the BLESSED VIRGIN MARY as mysteries which are important for redemption.