It has never been known as Fanshaw (apart from some cartoons in newspapers, Fanshaw is a surname it it's own right, and is no relation the Featherstonhaugh, or featherstonhoff, as sometimes written, as pronounced. If there is such a thing as the correct pronunciation it is known in the North East, the source of the surname, as Featherston haw, there are several place names ending in haugh, in the Tyne valley.