That's funny Cogito - I didn't realize it was so rare to hear. My grandparents were of Norwegian ancestory and my grandmother said "Ooftah!" often. It means the same thing as "Oh my goodness" or "Good grief" or like you said "Geez". It must be a Swedish saying too, which makes sense, since they have only been separate countries in recent history. It must be heard a lot in the areas of our country with larger concentrations of people with Scandanavian heritage. The word is used like crazy in Scandanavian jokes. It is spelled a lot of different ways... uff-da being used more often. Hah hah I sound like a linguist or something.
I do love to learn the background of things and we can see you do too.