See on Rom 11:25. The kindred word μεμύημαι I have been initiated (A.V., instructed) occurs Phi 4:12, in the sense drawn from the technical use of the term, denoting the induction into pagan mysteries. Ignatius addresses the Ephesians as “fellow-initiates (συμμύσται), or students of the mysteries, with Paul” (Ephesians, 12). In the New Testament the word implies something which, while it may be obscure in its nature, or kept hidden in the past, is now revealed. Hence used very commonly with words denoting revelation or knowledge. So, “to know the mysteries,” Mat 13:11; “revelation of the mystery,” Rom 16:25; made known, Eph 3:3, etc. In Colossians and Ephesians it is used, with a single exception, of the admission of the Gentiles to gospel privileges. Compare Rom 16:25, Rom 16:26.
From ages - generations (ἀπὸ - αἰώνων - γενεῶν)
The unit and the factors: the aeon or age being made up of generations. Compare Eph 3:21, where the literal translation is unto all the generations of the age of the ages. The preposition ἀπὸ from, differs from πρό before (1Co 2:7), as marking the point from which concealment could properly begin. Before the beginning of the ages of the world the counsel of God was ordained, but not concealed, because there were no human beings from whom to conceal it. The concealment began from the beginning of the world, with the entrance of subjects to whom it could be a fact.