What is an unknown tongue?

1 Corinthians 14:14 seems to show that the person who is speaking in an unknown tongue or in a tongue that is not to
be understood.

It seems to point out that the person himself does not understand what he is talking about, does not know what he’s
talking about.

However, that’s not what the verse is saying.

Answer: The person who is speaking in a tongue, it’s not known to the hearer, to the audience. It’s not understood, to the hearer to the audience.

Notice that the context of verse 9, verse 16 and verse 19 proves that the context is about the hearers in the audience who do not know, who do not understand what the person is saying in that tongue.

Hence, it is an unknown tongue.

Hence, it is a tongue that is not understood well, to the hearers.

Why?

Because that tongue is foreign, not understood.

Revelation, 7:9 proves that tongues are referring to different national languages.