This is a question I constantly ask myself when I consider what it would be like to start from scratch. My family lore gave me their ethnicity, but not everyone is that lucky. So, how do I know that my surname is Luxembourger?
The answer is that there's no easy answer. Most Luxembourgers immigrated to the United States sometime in the 19th century. During that century, Luxembourg had used both French and German as official languages. German names are more common, but that's no guarantee. The census can provide one hint. Look for a "Dutch" or Luxembourger ethnicity in an area with a lot of Germans. These individuals are likely Luxembourger. Remember to check all of the census documents for an individual. Depending on the enumerator, they could be recorded as German all but one time. Theresa Beckers offers some suggestions for reading on her webpage. The information is a bit outdated. The publications from the National Archives are no longer available. You can access the index to the Tables Decennales online. Consider looking at Luxembourg message boards and family sites as well. Patience will solve most problems.