Go back and watch Kill Bill: Vol. 1 again. The Bride's name is bleeped out every single time, but rather poorly. It's quite obvious that her name starts with a 'B', and ends with either an 'X' sound, or an 'S' sound. Combined with lip-reading, I had guessed that her name was "Beatrice" when I rewatched Vol. 1 before going to see Kill Bill: Vol. 2. The last name is hidden in plain sight, as Doches mentioned, but with everything else placed just so in the movies, I believe Tarantino wanted viewers to be able to guess it.