While on the topic of names, my wife Ariella has a post (link) on Eisav's wife Basmas being called Machalas in the parsha. Rashi explains that one's sins are forgiven on the occassion of marriage. Apparently this credit extended to Eisav as well, and hence his wife was called Machalas, from the term mechila, forgiveness.
Rashi is based on a gemara in Yevamos 62b: “Rav Chama bar Chanina said, once a man marries a woman, his sins depart, for it says, ‘One who has found a wife has found good and will draw ratzon [appeal] from G-d.’” Maharal explains that the idea of cheit = chisaron, incompleteness. Man is spiritually incomplete without a wife. Marriage removes the cheit, this state of incompleteness. The individual, thus transformed, has a new identity -- gone is the old self and its sins and imperfections.
I would suggest that it's not just the name Machalas, but the name change itself which underscores this point. As we discussed, the Ishbitzer identifies shem=ratzon (in gematriya). "Matzah isha matzah tov v'yafek ratzon m'Hashem" -- the finding of a wife releases an added measure of ratzon from Hashem. The recipient of that ratzon is imbued with a different identity, hence a different name.