When you can't find an ancestor by the name that you're familiar with...
I've had this problem with one (cough, cough, MANY) of my searches. I'll give you an example with a a couple of German names that I've had problems with-
Dewalt Bish married Mary Drawbond on Feb. 21, 1821 in Rockingham Co. VA. Now, I have a tendency to be like a hound dog and run off on tangents-I was curious about Mary Drawbond. What kind of name was 'Drawbond'? In the marriage record, it lists her father as Conrad Drawbond. So, I dug through more records and found a Conrad 'Traban' married to Mary Zieglerin. (Ziegler, the 'in' indicates in German that she's a woman). So, since this area of VA was predominantly German (many from the contested region of the Alsace Lorraine), I began to dig around and found the last name Trobaugh. So, we start with the German Trobaugh-they immigrated to the US and their names get anglicized by ministers and census takers to Traban and then Drawbond. And that happened in less than a generation. D and T's are regularly interchanged with German, and to a lesser extent, French names. Occasionally you'll see F's and V's as well with German. (and B's and V's in Spanish)
Why, you ask? A lot of our ancestors were illiterate. They knew their numbers but were unlikely to have gone to school-(a caveat here-they often sent as children to other families to learn a trade like baking or blacksmithing or shoemaking) I have yet to find an emigrant in my research that didn't make sure their children were educated to some degree. So, they couldn't, or didn't feel the need to correct the spelling.
German is an interesting language-and spelling it the way it was pronounced by a German speaker introduced many interesting interpretations. Plus you have High German (Switzerland and the Amish) and Low German (Germany, parts of the Alsace region of France), but this is not hard and fast.
My lesson here? Well, simply, ALWAYS check different spellings that can occur with a surname. Heck even with a first name, I had a Diebold turn into Dewalt-again, in one generation.
I hope that this helps you!