eponymist

Century Dictionary and Cyclopedia

1. n. One from whom a country or people is named; an eponymic ancestor, hero, or founder.

Wiktionary

1. n. One whose name is used as an eponym; a person after whom something is named.

GNU Webster's 1913

1. n. One from whom a race, tribe, city, or the like, took its name; an eponym.