Charles Ellicott Commentary Genesis 4:18

"And unto Enoch was born Irad: and Irad begat Mehujael: and Mehujael begat Methushael; and Methushael begat Lamech." — Genesis 4:18 (ASV)

Unto Enoch was born Irad. —Cain was building a city, ‘Ir, and this probably suggested the name ‘Irad. It has little in common with Jared, as it begins with a harsh guttural, usually omitted in English because it is unpronounceable, but which appears as g in Gomorrah. Possibly ‘Irad means citizen; but these names have been so corrupted by transcribers that we cannot be sure of them. Thus, here the Septuagint calls ‘Irad Gaïdad, and the Syriac ‘Idor. In the list that follows, the names Mehujael (Samaritan Michel, Syriac Mahvoyel), Methusael, Enoch, and Lamech (Hebrew, Lemech), have a certain degree of similarity to those in the line of the Sethites, from which many commentators have assumed that the two lists are variations of the same original record.

But it is usually a similarity of sound only, with a diversity of meaning. Thus Mehujael, smitten by God, corresponds to Mahalaleel, glory to God; Methusael, God’s hero, to Methuselah, the armed warrior. Even when the names are the same, their history is often very diverse. Thus, in the Cainite line, Enoch is initiation into city life, and in the Sethite line, into a life of holiness; and the Cainite polygamist Lemech, rejoicing in the weapons invented by his son, is the very opposite of the Sethite Lemech, who calls his son Noah, meaning quiet, rest.