The term 'synonym eponym' is composed of two words: 'synonym' and 'eponym'. A synonym is a word that has the same or nearly the same meaning as another word. An eponym is a person, place, or thing after which a particular name or thing is named or thought to be named. The crossword solution for this term is 'ROGET', which is the surname of Peter Mark Roget, a British physician, natural theologian, and lexicographer. Roget is best known for his thesaurus, which was first published in 1852 and is still in use today.