Mapping Your Surname. The origin of a surname can often be traced by plotting its present-day distribution on a map. For David Hey this led to the discovery of the exact Hey - an enclosed piece of land - which gave rise to the surname 700 years ago. Meanwhile, DNA analysis points to a single ancestorforthe surnames Blencowe and Foden, and to remarkably few ancestors for Redhead and perhaps even Smith. Dr George Redmonds investigates. Producer Sandra Sykes. E-MAIL: nature@bbc.co.uk