Stage name

Marilyn Monroe (born Norma Jeane Mortenson) created her stage name by combining her mother's maiden name with the first name of Broadway star Marilyn Miller.

A stage name or professional name is a pseudonym used by performers, authors, and entertainers—such as actors, comedians, singers, and musicians. Such professional aliases are adopted for a wide variety of reasons and they may be similar, or nearly identical, to an individual's birth name. Though uncommon, some performers choose to adopt their stage name as a legal name.

Nicknames and maiden names of individuals are sometimes used for this purpose.

From Wikipedia