E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
When Malcolm III. of Scotland invaded England, and reduced the castle of Alnwick, Robert de Mowbray brought to him the keys of the castle suspended on his lance; and, handing them from the wall, thrust his lance into the kings eye; from which circumstance, the tradition says, he received the name of Pierce-eye, which has ever since been borne by the Dukes of Northumberland.
This is all a fable. The Percies are descended from a great Norman baron, who came over with William, and who took his name from his castle and estate in Normandy.Sir Walter Scott: Tales of a Grandfather, iv.