Jamieson, Fausset and Brown on Genesis 11:7

7. confound their language--literally, "their lip"; it was a failure in utterance, occasioning a difference in dialect which was intelligible only to those of the same tribe. Thus easily by God their purpose was defeated, and they were compelled to the dispersion they had combined to prevent. It is only from the Scriptures we learn the true origin of the different nations and languages of the world. By one miracle of tongues men were dispersed and gradually fell from true religion. By another, national barriers were broken down--that all men might be brought back to the family of God.