What is a nomen nudum?

A nomen nudum (plural nomina nuda) is a term used for a name which is unavailable because it does not have a description, reference or indication (specifically a name published before 1931 which fails to conform to Article 12, or after 1930 but fails to conform to Article 13).

Nomina nuda and other unavailable names can be made available if they are published again in a way that meets the criteria of availability; however, they are attributed to the author who first made them available, not the person who first used them.