This name is VERY popular in many francophone countries, I knew many girls with this name abroad. There was a French girl who came to the U.S. the year before I left named Fanny and everyone made fun of her and slapped her butt. I can't imagine what they would be slapping in commonwealth nations. :-0
I would name my child Fanny if I lived in a francophone nation, other than the unfortunate association, it's really cute! Fanny is a very polite word for butt anyway!