The pirates of the days of yore lived completely beyond the laws of society, and as such, occasionally had the opportunity to create societies of their own with new norms and institutions that shocked more conservative and law-abiding folks. Surviving documents such as pirate constitutions and pirate law codes were often ahead of their time with their emphasis on equalitarianism and basic rights for all.
One of the more interesting institutions developed by pirates in the 17th century was the practice of matelotage, a formal, often contractual permanent union between two consenting adult men. These men, known as each other's matelot, jointly owned land and possessions, fought side by side, and nursed each other when ill. Matelots often drew up contracts stipulating that if one were to die, the other would inherit all his property, but even when contracts were not made, matelotage was such a prevalent practice that the surviving matelot was often awarded the property anyway.
In other words, matelotage was just like marriage, only between two men instead of a man and a woman.
And gay marriage is a lot older than some people think.
Matelotage is well documented in historical sources, and was well-known at the time. Matelotage was especially common on the pirate haven of Tortuga in the Caribbean, where one of the governors was so concerned about the practice that he imported hundreds of female prostitutes to try to lure men away from the arms of other men. But matelotage was also a common practice on several other islands where European women were hard to find, including Hispaniola and Jamaica.
The word matelot is a French term meaning "seaman" and matelotage means "seamanship" in French. But very early on the word was borrowed into English with the meaning of "buddy" or "comrade" and was eventually shortened to the word mate, so "matelotage" as an English word might best be glossed as "buddyship" or "comradeship."