Sorry, Yonks, this is no help with your query, but my father had a pal called Jimmy Rumgay in Dunfermline in the 1920s (he must have been born about 1902 I think).
He became so fed up with having to explain and spell out his unusual surname that, when asked, he often gave his name as: "White - W. H. I. T. E."
I don't suppose he knew that he might have had an ancestor called Black.