There exists a genforum.genealogy.com Lum Family Genealogy Forum (I'm not a member) that connects "Lum" to "Lom" and "Lombe". See http://www.surnamedb.com/Surname/lumm#ixzz15WNHdS5L
. I've also done a lot of research on this name. My family is a Jewish family from the shtetl's of E. Europe which immigrated to Chicago starting in the 1880's. However, it was connected to a family of the same name that immigrated here earlier from Baden-Wurttemburg. The name appears as a location name throughout the Germanic world, in Norway, Silesia, and the Low Countries. In addition, there are hundreds of entries for Lome / Lum / Lom in UK records going back centuries--the earliest I've found are in the 12th century. I believe there exists a connection between these names and "Lombard" and "Lambert". In Yiddish, "Lom" is a Low German form of "Lamm", meaning "lamb". "Lamb" is not Indo-European in origin--it only exists in Germanic languages but not in any other branch, so like many German words came from some older language family that merged with an Indo-European dialect to form proto-Germanic. The original referents of "Lom" all I think pertained to an Old European pastoral population that spoke such an older language. Somehow, we should integrate our efforts. Evidently, genforum is now part of Ancestry also.