With respect to piracy, I was surprised when I found this site:
I have no idea how valid their claims are for the history of the Jolly Roger. The story they give has shades of the conspiratorial, especially with the claims of connections between the Knights Templar (originators of the skull-and-crossbones motif), the Freemasons, and the royal families of England and Scotland.
Piracy does have a strange attraction. Kind of like the lawlessness of Robin Hood--a villain who was morally equal to (or better than) the law-men.
I don't quite know what to make of that idea.