From Citizendium, the Citizens' Compendium
An eponym is the name of a person which has been applied to some non-personal thing of significance, most often a work of literature, a scientific invention, or a geographical discovery. The person and the thing are then said to be "eponymous"; such is the relationship between Henry Hudson and Hudson Bay, Aeneas and the Aeneid, and Guglielmo Marconi and the Marconigram (an early proprietary name for a telegram). Self-titled books, such as Mark Twain's Huckleberry Finn, Henry Fielding's Tom Jones, or any of J.K. Rowling's Harry Potter books have eponymous heroes. Coinages which derive from personal names -- such as "Jeffersonian," "Bowdlerize," or "Monicagate," are also, in a slightly different sense, eponyms. In certain areas of nomenclature, the name of the discoverer of a biological species, an element, or or phenomenon, is similarly given eponymous credit, for instance the element Einsteinium, the Van Allen Belt, or the scientific names of most species, in which the discoverer's name precedes the decsriptor, e.g. Carolus Linnaeus, whose surname, usually abbreviated as "L.", precedes thousands of biological names whose type and nomenclature he established.