Might be regional but fanny is definitely slang in the US as well, but very quaint/dated, meaning butt. Would generally be used in some sort of context like a grandma telling a kid, 'Get your fanny over here right this second!'
It would never be offensive or used with sexual connotation. It's kind of like the equivalent of wiener.
It would never be offensive or used with sexual connotation. It's kind of like the equivalent of wiener.