(Will appear in the September 2008 issue of Community News)
An eponymous person is the person something is named after. For example, Hamlet is the eponymous protagonist of Shakespeare's play of the same name. Queen Victoria is the eponymous monarch who reigned during the Victorian age. Andrew Jackson is the eponymous American president whose political philosophy is known as Jacksonian Democracy. The practice of using a famous name to refer to something is ancient, but the word eponymous only dates to the middle of the 19th century. What's curious is that in recent times, the word has begun to be used to refer to the thing being named, instead of to the person. If opera singer John Hugevoice puts out a CD named John Hugevoice, you might hear the CD referred to as eponymous. But that's hugely wrong. It's the man who's eponymous, not the CD.
I'm collecting all of these at: http://www.dvorkin.com/davidsdefs.html