Considering the international circles I mix in, I'd avoid it like the plague and consider it cruel and unusual punishment. It's kind of an older name (could be used a nickname for
Francis, though I like Franki better) and its current use as crude slang makes it kind of a no go as an official name. I remember a British guy I met in BC saying he couldn't very well move to
Fanny Bay because his mum would never send him mail there.
I suppose if your child is never going to leave N.
America, you may be able to get away with it, but it's prob'ly recommendable these days to make it a nn for something (like
Francis or
Francesca) rather than making that the child's official name on the b.c. 'cause she may not want to go by that later. (esp. if she ever leaves the continent)
A few years back, I was explaining to an American at a camp weekend why I now refer to bum bags rather than fanny packs and suddenly heard hysterical laughter from a Northern Irish gal in the next room over (thin doors) who overheard the conversation and had never heard the term fanny pack before.