I have a birthmark on my knee...My Poppy always said my mother marked me as a baby because someone offered her peanuts when she was pregnant and she didn't eat it It is shaped like a small peanut out of the shell...The Old Italians believe that you Mark the Baby if you don't at least taste everything you are offered while pregnant.
I have two. A very small one on my left calf, slightly below my knee. It's darker in colour than my normal skin colour so that's how I noticed it.
My other birthmark is huge. It goes from my right elbow up my arm and about half way across my back. When I was in school and wore a tank top people would always ask me if I was dirty. it doesn't cover the whole arm, looks kind of like a trail ha ha. I have always been very proud of my birthmarks.