if your going Xaela you can pretend your last name is a tribe that has long been forgotten or appropriated into another tribe. just like what was said in the naming conventions

"The Othardian steppe is a vast region, therefore, every so often, one may come across a Xaela with a surname that is not found on the list of 51. This may mean that they are from a clan that was recently destroyed or absorbed. It may mean that they are of a new tribe that was formed by members leaving another. It may mean they are of a tribe that remained hidden in the northern mountains."