Surnames and DNA Confusion

[Castlebob]

It's often worth querying tags people attach to various surnames. I've lost count of the number of times I've read of the Percy family of Northumberland being 'of Norman stock'. The earliest Percies, who arrived in Yorkshire via Normandy, fitted that description but their line daughtered out in the 12th C.
However, Agnes, Baroness de Percy wed Josceline de Louvain, a Fleming who adopted the Percy surname. He quartered his Flemish lion rampant arms with those of the Percy five fusils.
I've researched several surnames who carried the Percy fusils in their coats of arms who actually used a non-Percy surname. I've seen some of these listed as their own surname with 'alias de Percy' added.
I mention the above as it shows how difficult it is to link surnames to Y-DNA. Burke's Peerage is a work that is often mentioned as 'proof' of a family's lineage, but I have seen errors in that. One line of a family I've researched was totally ignored in the tome, and further delving revealed that the branch had been 'overlooked' as the eldest son had wed a barmaid! Sir Bernard Burke sometimes had to rely on the family he was recording supplying him with info, hence ommissions of the sort I've described.
I've seen a number of Cumbrian families where one brother took his father's surname, and the other took the mother's maiden name. If you throw in the habit of using the place of residence as a surname, then confusion as to family links can really set in.
The good news is that Medieval records do reveal clues as to some individuals' true roots. It's just frustrating that many of these are buggers to decipher & generally pretty dull reading!
Bob