Apparently, for years Jon has replied - jokingly - that it's an old Irish name, from County Mayo. Ironically, current research into the Sirdevans of Mayo may just prove an Irish link to our Surdevan family. Time will tell.

Old English/Old French?
Some time back, in the 70's I think it was, I wrote to a firm called Family Crests Co. Ltd. to see if they could come up with anything about the origins of our family name. Unfortunately, their reply was too vague, and I didn't take up their offer to buy a family crest for the princely sum of £24.95 "for two".
Nevertheless, the information they supplied is of some interest, and is therefore reproduced below.

Tony.