The Greek word anexichniastos

Found just twice in the New Testament (Rom. 11:33; Eph. 3:8), the Greek adjective “anexichniastos” meant “unsearchable,” past finding out,” or “incomprehensible.”

Paul used this term to say “perceptible history does not lead even to the tracks of the true ways of God” (Exegetical Dictionary of the New Testament, 1:97). Stated another way, our wisest and smartest ideas and plans are woefully inadequate to really grasp who God is and what He has done unless He reveals this information to us.