'Hidden' in the Bible

“Anyone who has an ear should listen to what the Spirit says to the churches. I will give the victor some of the hidden manna. I will also give him a white stone, and on the stone a new name is inscribed that no one knows except the one who receives it.

but in the days of the sound of the seventh angel, when he will blow his trumpet, then God’s hidden plan will be completed, as He announced to His servants the prophets.”