So I just learned on the propaganda "History" Channel show The Curse Of Oak Island S06E06 that the pirate flag with the Jolly Roger skull and crossbones is actually representative of the Templar Knight Order's patron saint, John The Baptist, who was beheaded according to legend and scripture. When the Templars we forced to disband, many disgruntled then became pirates - same occupation, different title. So it was originally a Templar symbol before it was pirate symbol, or a Yale "Skull & Bones" symbol. Not really a surprise. The Nazi SS used it. Now some military units and/or mercenaries have it, or variations of it, on patches.

I actually like that show despite myself. And I know the "History" Channel can be trusted as far as you can throw it. Find me a way to get a good grip on it and I'll try to throw it in the trash can (except that show, it's good timesuck/background noise).