St. John Chrysostom, Homily 21 on Genesis:

Perhaps, however, someone may say, How did Lamech come to have such a degree of prophetic power? After all, Scripture doesn't record that he was a person of virtue and remarkable powers does it? Don't be surprised at that, dearly beloved: the Lord, in his wisdom and inventiveness, frequently permits great and wonderful events to be foretold by unworthy people, not only in the Old Testament but also in the New. I mean, listen to the evangelist's words about Caiaphas, the highpriest of the Jews: "He did not give this as a personal opinion, but in his capacity of highpriest that year he prophesied that Jesus was destined to die, not for the person alone but to bring together into one also the nations that had been scattered." You will find something like it occurring again in the story of Balaam also: when urged to curse the people, he not merely did not curse them but even prophesied great and wonderful things, not merely about the people but also about the coming of the Saviour. So don't be surprised if in this case also Lamech in naming his child gives him a name of this kind; instead, attribute it all to God, who arranges everything in his inventive wisdom.