E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Hackum (Captain).
A thick-headed bully of Alsatia, impudent but cowardly. He was once a sergeant in Flanders, but ran from his colours, and took refuge in Alsatia, where he was dubbed captain. (Shadwell: Squire of Alsatia.)