Chapter 15 — Part II: The Sacraments — Introduction on the Sacraments in General
Section 4. But by the Latin Fathers who have written on theological subjects, the word sacrament is used to signify a sacred thing which lies concealed. The Greeks, to express the same idea, made use of the word mystery. This we understand to be the meaning of the word, when, in the Epistle to the Ephesians, it is said: That he might make known to us the mystery (sacramentum) of his will; and to Timothy: great is the mystery (sacramentum) of godliness; and in the Book of Wisdom: They knew not the secrets (sacramenta) of God. In these and many other passages the word sacrament,- it will be perceived, signifies nothing more than a holy thing that lies concealed and hidden.