There is no evidence at all that Paul meant anything other than languages--at a minimum he knew Hebrew, Greek, Aramaic, Latin. In the research I have done, I have never found a secular passage (certainly not a bible passage) where he Greek word glossa, used here, meant unarguably anything other than known languages.Yet he thanked God that he spoke in tongues. Hmmm....
1 Corinthians 14:4-5,18
[4]A person who speaks in tongues is strengthened personally, but one who speaks a word of prophecy strengthens the entire church.
[5]I wish you could all speak in tongues, but even more I wish you could all prophesy. For prophecy is greater than speaking in tongues, unless someone interprets what you are saying so that the whole church will be strengthened.
[18]I thank God that I speak in tongues more than any of you.
I challenge you to find a secular Greek source or author where glossa means some kind of ecstatic prayer language--perhaps in the Greek mystery religions?