I wish I could say for sure that I know where your Clement come from, but I cannot. I do have Clement in my line, but the represent a present wall (not sure if it is brick or just vegetation!). And Clement would seem to be a common name.
My family originates in Meix-le-Tige just southwest of Arlon. One of the families is made up of a Bailleux father and Clement mother. I am not sure where her Clement family is from. However, one of her daughters married a Clement from Baranzy which is SSW of Meix-le-Tige and certainly in the wrong direction from Nothomb.
I may not be able to give you any help but would hope that at least I can give you some good incentive. Good luck.