Yes, I do know that Oma is a German word for grandmother, though as I don't speak German I didn't know what it was short for. (so thank you for that.) Odd thing about Aunt Oma is that as far as I know she was called this from the time she was at least 15 or 16 years old. Maybe she was a "mother" to younger siblings, or maybe it is short for something else. The two girls in the family were confusingly (to me) named Hettie and Hattie, so it also may have been a way to distinguish them.