Today’s Catechism sections discuss the word “Amen”. Supporting material comes from the “Catholic Encyclopedia”.

"Amen"

1061 The Creed, like the last book of the Bible,644 ends with the Hebrew word amen. This word frequently concludes prayers in the New Testament. The Church likewise ends her prayers with "Amen."

1062 In Hebrew, amen comes from the same root as the word "believe." This root expresses solidity, trustworthiness, faithfulness. And so we can understand why "Amen" may express both God's faithfulness towards us and our trust in him.

1063 In the book of the prophet Isaiah, we find the expression "God of truth" (literally "God of the Amen"), that is, the God who is faithful to his promises: "He who blesses himself in the land shall bless himself by the God of truth [amen]."645 Our Lord often used the word "Amen," sometimes repeated,646 to emphasize the trustworthiness of his teaching, his authority founded on God's truth.

1064 Thus the Creed's final "Amen" repeats and confirms its first words: "I believe." To believe is to say "Amen" to God's words, promises and commandments; to entrust oneself completely to him who is the "Amen" of infinite love and perfect faithfulness. The Christian's everyday life will then be the "Amen" to the "I believe" of our baptismal profession of faith:

May your Creed be for you as a mirror. Look at yourself in it, to see if you believe everything you say you believe. And rejoice in your faith each day.647

1065 Jesus Christ himself is the "Amen."648 He is the definitive "Amen" of the Father's love for us. He takes up and completes our "Amen" to the Father: "For all the promises of God find their Yes in him. That is why we utter the Amen through him, to the glory of God":649

Through him, with him, in him,
in the unity of the Holy Spirit,
all glory and honor is yours,
almighty Father,
God, for ever and ever.
AMEN.

The “Catholic Encyclopedia” describes the word “Amen” in this way:

The word Amen is one of a small number of Hebrew words which have been imported unchanged into the liturgy of the Church, propter sanctiorem as St. Augustine expresses it, in virtue of an exceptionally sacred example. "So frequent was this Hebrew in the mouth of Our Saviour", observes the Catechism of the Council of Trent, "that it pleased the Holy Ghost to have it perpetuated in the Church of God". In point of fact St. Matthew attributes it to Our Lord twenty-eight times, and St. John in its doubled form twenty-six times. As regards the etymology, Amen is a derivative from the Hebrew verb aman "to strengthen" or "Confirm".

Footnotes

644 Cf. ⇒ Rev 22:21.
645 ⇒ Isa 65:16.
646 Cf. ⇒ Mt 6:2, 5, ⇒ 16; ⇒ Jn 5:19.
647 St. Augustine, Sermo 58, 11, 13: PL 38, 399.
648 ⇒ Rev 3:14.
649 ⇒ 2 Cor 1:20.