Generations— תולדות Toldoth, sometimes signifies the origin of the thing treated of, and sometimes the posterity of those who are mentioned. Here it means the origin, or successive production, of the world; as much as to say, "this is the true and faithful account of the origin," &c.
Lord— By this word our translators have chosen to render, throughout their translation, יהוה Jehovah, the peculiar and appropriated name of God; which first occurs here, but will be explained more suitably when we come to the third chapter of Exodus, and the 15th verse. It is joined with אלהים Elohim here, Jehovah Elohim, by apposition, says Le Clerc, to shew, that the God (Elohim) who created the world is the same Jehovah whom the Israelites worshipped. The Hebrew Doctors observe, that Jehovah Elohim, Lord God, is the full and perfect name of God; and therefore fitly reserved to this place, when the works of God were perfected.