'Unknown' in the Bible

For he who speaks in an unknown tongue is not speaking to men, but to God; for no one understands him. Yet in the Spirit he is speaking secret truths.

He who speaks in an unknown tongue does good to himself, but he who prophesies does good to the Church.

For if I pray in an unknown tongue, my spirit prays, but my understanding is barren.

but in the Church I would rather speak five words with my understanding--so as to instruct others also--than ten thousand words in an unknown tongue.

In the Law it stands written, "'By men of unknown tongues and by the lips of an unknown nation will I speak to this People, but even then they will not listen to Me', says the Lord."

If there is speaking in an unknown tongue, only two or at the most three should speak, and they should do so one at a time, and one should interpret;