In 7th grade (too many years ago) I had a History teacher that liked to do historical simulations. One of these was the Constitutional Convention of 1789 where each student played one of the delegates. I played the delegate "Coatsworth Mifflin". My friends seemed to think it was funny so they started calling me Mifflin, and it stuck. I've since used it as my 'handle' on many message boards over the years.