E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Duke of Gascony. One of Charlemagnes knights, and the most treacherous of all, except Ganelon. He sold his guest and his family. He wore browned steel armour, damasked with silver; but his favourite weapon was the gallows. He was never in a rage, but cruel in cold blood.
It was Wolf, Duke of Gascony, who was the originator of the plan of tying wetted ropes round the temples of his prisoners, to make their eyeballs start from their sockets. It was he who had them sewed up in freshly-stripped bulls hides, and exposed to the sun till the hides in shrinking broke their bones.Croquemitaine, iii.