And the firstborn bare. This was a terrible blindness, that the daughters of Lot, shaking off all feeling of shame, raised up a memorial of their virtue, and through an eternal sign have exhibited their dishonor before their posterity. To their sons, or better, two nation in their persons, they give names, whence everybody can know that it was a family, originating from adultery and unchaste intercourse. The eldest boasts that she had obtained her son from her father, the other that her son was born of close relationship. Thus both unashamedly spread their crime, while they rather, through shame of their crime, had hidden themselves in eternal hideouts. Not content with the infamousness in their time, the propagate their crime into other times. Therefore, there is no doubt that they, enchanted by satan, have forgotten all difference between what is scandalous and honest. Paul says, (Romans 2:5,) that wicked, after a long pleasure in sinning, are at the end deprived of all feel of grief thereof. Such stupidity undoubtedly had caught those girls, because they did not shame themselves to spread their dishonor everywhere. Further, such an example of God's punishment is revealed us, in order that we not allow any sin, and we will not lose ourselves in licentiousness, but that we, through fear of God, spur ourselves on to penitence.

Called his name Moab - This name is generally interpreted of the father, or, according to Calmet, מואב Moab, the waters of the father.

And the firstborn bare a son, and called his name Moab: the same [is] the father of the (s) Moabites unto this day.
(s) Who as they were born in most horrible incest, so were they and their posterity vile and wicked.

And the firstborn bare a son, and called his name Moab,.... As if it was "Meab", from the father, as Aben Ezra, and so Josephus, that is, which she had by her father; and she was so far from being ashamed that it might be known in time to come, she gave him this name. Hillerus (w) makes it to be a compound of and and to signify "going into", or "lying with a father", which still more notoriously points to her own action. Drusius has another derivation of the word, at least proposes it, and renders it "aqua patris"; "mo" in the Egyptian language signifying "water", which is sometimes used for seed, see Isaiah 48:1,
the same is the father of the Moabites unto this day; a people that lived on the borders of the land of Canaan, often troublesome to the Israelites, and frequently spoken of in the Old Testament.
(w) Onomastic. Sacr. p. 414.