E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A Burgundian blow, i.e. decapitation. The Duc de Biron, who was put to death for treason by Henri IV., was told in his youth, by a fortune-teller, to beware of a Burgundian blow. When going to execution, he asked who was to be his executioner, and was told he was a man from Burgundy.