There were old English swear phrases that referred to the Crucifixion, e.g., "by God's blood", "by God's wounds" and "by God's hooks". These were abbreviated to "zblood". "zounds" and "gadzooks". These are all obsolete, except the first one, which has survived as "bloody", so yes, it is a goddam swear word, and I'm surprised at you, Virginia, for using such language!
As for pirates, well, that's partly a matter of definition. The "Dunkirkers" were privateers in the service of Spain from the late 1500s to the mid-1600s.
In the late 1600s, Dunkirk was the base of French corsairs, the most famous of whom was Jean Bart.
And there was also the American Revolution privateer, Gustavus Conyngham, known as the 'Dunkirk Pirate'.