Your first submissive letter be to Master or Mistress name, where name is your partner's real name.
The dominant may choose whatever name he or she wants, and the dominant may also change the submissives name. The submissive should accept all new names.
Names are symbolic and meaningful, and they help keep roles straight.
If your submissive wants a humiliating name, you should also use his or her real name, uncapitalized. See Splitting.