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 may be similar or nearly identical to an individual's birth name or be inspired by nicknames or maiden names. Some performers choose to adopt their stage name as a legal name.

From Wikipedia