While the Pottruff name first originated in Pennsylvania (around the 1800's), you'll find the bulk of "Pottruff's" are living in southern Ontario (and in particularly Hamilton). There's even a street named Pottruff in the city.
I did a lot of research looking through family records going back more than 150 years. Also have a few family members that preserved several records (as does the city of Hamilton). The name is of english origin comming from "Potter" and "Woodruff" (or Potter-Woodruff). For many of years the name was hyphenated until one of our relatives decided to "merge" the names into "Pottruff".
To test this hypothesis, try finding "Pottruff's" in any other country (i.e. Germany, England, wherever). What you'll find is that the name is unique to Canada and the US. If the name was of German heritage, you should find alot of "Pottruff" in this country (name comes up empty). However Potter and Woodruff are very prolific in the UK.