How do we know that tongues were actual languages?

The evidence of tongues being known languages is found in the accounts of Acts 2, where individuals from different nations recognized their own languages being spoken. The amazement of the crowd highlights that these were not unintelligible, gibberish sounds but rather articulate languages conveying the wonderful works of God. Furthermore, Paul emphasizes in 1 Corinthians 14 that language serves a purpose of communication and edification, reinforcing the idea that tongues should be understandable and meaningful rather than nonsensical babble.