Their theory is based on an earlier Madoc being the one that legends were about. They are also keen Arthurian researchers.
The Madoc legend was revived by Dr. Jon Dee to support British claims to America and dispute the Spanish claim in the time of Elizabeth I but there is much confusion over the literary references he used to establish this claim.
Mad Doc - like the Dog river in Alabama which used to be called the Maddog river. Supposedly named for Madoc. Mobile bay being where he landed
ap is just Son of like Mac in Irish or Scotts
Owain - Oh Wine
Gwynedd - the tough one Gwin edth - the dd is a ddddhhhh sound
Like Button Gwynett - signer of the declaration of independence another Welshman
More Welshmen signed the declaration than any other extraction. You can keep Columbus Day too, even though he swore he had discovered India and refused to set foot on the mainland.