'Unknown' in the Bible

For they heard them talking in [unknown] tongues (languages) and exalting and magnifying and praising God. Then Peter said,

For as I passed by, and beheld your devotions, I found an altar with this inscription, TO THE UNKNOWN GOD. Whom therefore ye ignorantly worship, him declare I unto you.

And when Paul laid his hands on them, the Holy Spirit came on them, and they began speaking in [unknown] tongues (languages) and prophesying.