Source : Webster's Revised Unabridged Dictionary (1913)

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.

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

Source : WordNet®

eponym
     n 1: the name of a person for whom something is supposedly named;
          "Constantine I is the eponym for Constantinople"
     2: a name derived from the name of person (real or imaginary)
        as the name of Alexandria is derived from the name of its
        founder: Alexander the Great