'Secret' in the Bible

But he is a Jew who is a secret one, whose circumcision is of the heart, in the spirit and not in the letter; whose praise is not from men, but from God.

For it is my desire, brothers, that this secret may be clear to you, so that you may not have pride in your knowledge, that Israel has been made hard in part, till all the Gentiles have come in;

Now to him who is able to make you strong in agreement with the good news which I gave you and the preaching of Jesus Christ, in the light of the revelation of that secret which has been kept through times eternal,