The name of a person for whom something is supposedly named

Gabriel Fahrenheit or Anders Celsius

Penn, to Pennsylvania

Rob Roy or Shirley Temple

The Earl of Sandwich, for one

Louis Braille or Louis Chevrolet

Earl of Sandwich, e.g.

James Parkinson or Alois Alzheimer

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

Name source

Name giver of a sort

See 16-Across

Person for whom a nation or city is named

Name giver

Columbus, to Colombia, e.g.

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Eponym \Ep"o*nym\, Eponyme \Ep"o*nyme\, n. [Cf. F. ['e]ponyme. See Eponymous .] 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. A name, as of a people,...

Wiktionary Word definitions in Wiktionary
n. 1 The name of a real or fictitious person whose name has, or is thought to have, given rise to the name of a particular item. 2 A word formed from a real or fictive person’s name.

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
one whose name becomes that of a place, a people, an era, an institution, etc., 1833, from Greek eponymos "given as a name, giving one's name to something," as a plural noun (short for eponymoi heroes ) denoting founders (legendary or real) of tribes, cities,...

WordNet Word definitions in WordNet
n. the name of a person for whom something is supposedly named; "Constantine I is the eponym for Constantinople" 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...

Wikipedia Word definitions in Wikipedia
An eponym is a person, place, or thing for whom or for which something is named, or believed to be named. For example, Elizabeth I of England is the eponym of the Elizabethan era . Many genericized trademarks such as aspirin , heroin and thermos are based...