eponymist

from The Century Dictionary.

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

from the GNU version of the Collaborative International Dictionary of English.

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

from Wiktionary, Creative Commons Attribution/Share-Alike License.

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