A document issued by a government in a time of war allowing private ships to attack the ships and seize the property and citizens of a hostile nation.
A former government document authorizing an individual to make reprisals on the subjects of an enemy nation, specif. to arm a ship and capture enemy merchant ships and cargo.
Origin of letters-of-marque
Middle English letters of mark from
Old French marque mark, seizure, reprisal marquetry
American Heritage Dictionary of the English Language, 5th Edition