E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Stabbed with a Bridport dagger, i.e. hanged. Bridport, in Dorsetshire, was once famous for its hempen goods, and monopolised the manufacture of ropes, cables, and tackling for the British navy. The hangmans rope being made at Bridport gave birth to the proverb. (Fuller: Worthies.)