'Unknown' in the Bible

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

Now as I was going along and carefully looking at your objects of worship, I came to an altar with this inscription: ‘TO AN UNKNOWN GOD.’ Therefore what you already worship as unknown, this I proclaim to 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.