How would anyone reading the following Greek know that the tongue mentioned in the verse is an unknown tongue?
14:2 ὁ γὰρ λαλῶν γλώσσῃ οὐκ ἀνθρώποις λαλεῖ ἀλλὰ τῶ θεῷ· οὐδεὶς γὰρ ἀκούει πνεύματι δὲ λαλεῖ μυστήρια·
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.
14:2 ὁ γὰρ λαλῶν γλώσσῃ οὐκ ἀνθρώποις λαλεῖ ἀλλὰ τῶ θεῷ· οὐδεὶς γὰρ ἀκούει πνεύματι δὲ λαλεῖ μυστήρια·
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.