In talking about John Montagu, the fourth Earl of Sandwich, Marciano states the following:
For the record, here are the definitions that lend themselves to the success of the portmanteau word: (from http://www.thefreedictionary.com)
adj. Of, relating to, or constituting an eponym.
n. A word or name derived from the name of a person.
adj. Having an unknown or unacknowledged name
It really is a fun word to say. Give it a try...anonyponymous