I was told that an author of books, who recently died, had a pseudonym. His antonym was John Murnion. Anyone know his pseudonym?

Hi Nonny
Try a good bookstore, esp a good used bookstore and they may be able to look it up for you in the publishers guide or whatever their big magic book is called.
Then come back and play with us in some of the other forums. This one isn't checked as often as the others above.