The Collaborative International Dictionary of English v.0.48:

Eponym \Ep"o*nym\, Eponyme \Ep"o*nyme\, n. [Cf. F. ['e]ponyme.
   See Eponymous.]
   1. The hypothetical individual who is assumed as the person
      from whom any race, city, etc., took its name; as, Hellen
      is an eponym of the Hellenes.
      [1913 Webster]

   2. A name, as of a people, country, and the like, derived
      from that of an individual.
      [1913 Webster]