I am a descendant of Johann Daudel who emigrated in 1913 to America from Temesvar, Hungary (now Timosoara, Romania, after WWII). He was of German ancestry and I'm still deep in researching how the family name was changed, but have recently uncovered some more clues after years of trying every soundex search I could think of, and only recently finally located how the family came over in batches in 1913. What is clear, is they were consistently spelling their last name as Tandl on each ship's manifest, and when their first child in America was born in 1915 shortly thereafter, he was recorded as a Tandl. The family name was recorded as Daudel at the next child's birth in 1919 (my grandfather), and in the 1920 census they were Dandel, in the 1930 census it's Dawdel or Daudel. When Johann (Tandl) Daudel died in 1936, he was clearly a Daudel on his death certificate, and that is the spelling the family kept thereafter.
(It doesn't help that Johann Tandl got lumped in with Croatians on the ship's manifest on his 1913 journey, but it's clearly him - right town and relatives back home to contact, wrong country recorded by clerk. He also was uniquely noted to have been to America before, and I'm still searching for his other earlier crossings.)
Part of the family lore is they were supposed to be French, and they changed the name from Dautel to Daudel, but I am starting to think it more likely that it was something more like Taudl/Daudl, and with a heavy German accent, so Daudl would have a T sound and "sound" like "toddle". Daudel was not pronounced by the family as "daw-dell" in a French way, it was spoken as "dawdle", much more German sounding.
I have become very interested in genetic genealogy and have had my DNA tested by 3 companies so far, and have definite proven links back to Germany, Prussia, and Hungary (and the Ukraine from a resettlement of Germans to Russia to North Dakota - Bessarabian Germans), and my wandering German ancestors were always migrating, usually looking for a better farming opportunity. I would not be surprised if my Tandl/Daudels were from eastern France from around the 1600s, passed through Austria on the way to Hungary, and married into German families. The farther eastern parts of France had borders that would change, so, France/Germany/Austria (Prussian empire)... my DNA seems to point to this region. There are also Daudels (further name change from Daudelin) in Germany that are of French origin... the story behind that has something to do with probably being Huguenots and fleeing France around 1685 to Prussia - one part of the family stayed in France, the rest left.
At this point in my research, I have to track down church records in Romanian archives of the Banat region of what was Hungary (under Austrian rule) from the 1700s-early 1900s, to try to get more concrete evidence about my Tandl/Daudels. If anyone has any further light to shed on these surnames and variations, or on research in these areas, I'm happy to share info.