- a person, real or imaginary, from whom a place or thing takes or is said to take its name: Brut, the supposed grandson of Aeneas, is the eponym of the Britons.
- a word based on or derived from a person's name.
- any ancient official whose name was used to designate his year of office.
- a name, esp a place name, derived from the name of a real or mythical person, as for example Constantinople from Constantine I
- the name of the person from which such a name is derived
