Why is the word unknown italicized in 1 Corinthians 14:2?

In 1 Corinthians 14:2, 'unknown' is italicized because it was added by the translators; it is not in the original text. The King James translators inserted it since they did not know how to handle the singular word 'tongue,' which denoted a guttural sound without phonetics or pronunciation.

Les explains that before verse 2, he notes the word 'unknown' is italicized, meaning it was added by the translators. He says even back at the time of the King James translators, they really didn't know how to handle this word 'tongue' in the singular. The term denoted a sound that had no phonetics to it; it could not be reduced to writing. It was just a guttural sound, and it had no pronunciation.

1 Corinthians 14:2

For he that speaketh in an unknown tongue speaketh not unto men, but unto God: for no man understandeth him; howbeit in the spirit he speaketh mysteries.

What kind of sound was the tongue spoken of in 1 Corinthians 14?

The tongue in 1 Corinthians 14 denoted a guttural sound that had no phonetics to it. It could not be reduced to writing and had no pronunciation. The word "unknown" is italicized because translators added it, as they struggled to handle the singular "tongue."