"Sir Pagan D'Urberville, that renowned knight who came from Normandy with William the Conqueror"
William the Conqueror on the Bayeux Tapestry
Hardy sets up the opposition between Christian theology and Pantheism
on the first page by naming the D'Urberville's fictional ancestor 'Pagan', a term for someone who follows a religion outside Christianity, particularly one that links spirituality with Nature. Hardy later calls Tess a "child of the soil", suggesting that she, like her ancestor, is much more attuned to earth religions than anything found in The Bible.
Unlike Sir Pagan, William the Conqueror was very much a real-life character. He invaded Britain in 1066 and fought the Battle of Hastings, defeating the army of King Harold. The battle was recorded in the Bayeux Tapestry.