These terms mean "a name used by an author instead of his real name": The nom de plume (or pseudonym or pen name) of William Sidney Porter was 0. Henry. Pen name is a literal translation of the French nom de plume; pseudonym is a Greek word for a fictitious name used to conceal identity. Nom de plume and pen name are usually restricted to the names of writers, whereas pseudonym can refer to a name assumed by anyone.
Dictionary of problem words and expressions. Harry Shaw. 1975.