The word "cognominate" refers to naming or identifying something or someone by using two names or combining two words. To find antonyms for this word, we can consider words that refer to giving one name to something or someone. Some of the antonyms for "cognominate" include "moniker," which refers to a single name or nickname used to identify a person or object, and "label," which often refers to a written or printed word or phrase used to identify something. Other antonyms might include "unidentifiable," "anonymous," or "unnamed," which all suggest the absence of a specific or recognizable name or identity.