Definitions of fanny:

• noun:   the fleshy part of the human body that you sit on

  Example: "Are you going to sit on your fanny and do nothing?"

• noun:   external female sex organs

  Example: "In England `fanny' is vulgar slang for female genitals"

• name:  A female given name (rare: 1 in 11111 females; popularity rank in the U.S.: #974)
• name:  A surname (very rare: popularity rank in the U.S.: #51934)