Hi Rick, (and others)
As has been pointed out the first written records of Morris were aout 14th century and I don't think it had anything to do with Paganism. Just borrowed a book from library on Morris from 1600-1900 which looks interesting and seems to put an end to many of the myths. (Author - Keith Chandler). Another book by John Forrest is on Morris between 1450 and 1700. Haven't been able to borrow a copy yet.
So where did it come from and why do it? As one quote I read from the turn of the century, when some old codger was asked - "it's just a good excuse for a piss-up"
As for pagans - many do do Morris - we have our fair share on my Morris team (which, incidently doesn't include me), including a High Priestess in the Wiccan Church of Canada (who you may know).
Also, in N. America anyhow, Morris Dancing attracted a lot of people also involved in the SCA (Society of Creative Anachronism). In general, I would say, it has attracted people from a broad set of backgrounds.