In his Autobiography, Jefferson wrote:
The tradition in my father’s family was that their ancestor came to this country from Wales, and from near the mountain of Snowdon, the highest in Gr. Br. I noted once a case from Wales in the law reports where a person of our name was either pl. or def. and one of the same name was Secretary to the Virginia company. These are the only instances in which I have met with the name in that country.