You really made my Friday with that one, reader Bernard. It all has to do with the fact that in the Colonial era rum was liquid currency. Most of us remember from our elementary school days that rum was the official spirit of the triangle trade, whereby slaves were taken from Africa to the Caribbean to work on sugar plantations, the sugar (and molasses and rum) went back to Europe, where it was traded for manufactured goods, which were taken to Africa to trade for more slaves, and so on and so on.
Then, rum was more valuable by weight than any other commodity save for gold. It kept indefinitely and like the American Express card it was recognized at over 15 million locations worldwide. For a short time the English government even recognized rum as money, which no doubt made banking more fun.
As highly valued and widely transported as rum was, it made an excellent target for privateers. What were privateers? Think of them as early military contractors: government-paid out-of-uniform toughs who sailed the seas settling scores, exacting retribution and collecting debts on behalf of their masters (unofficially, obviously). As you can imagine privateers tended to amass quite a lot of loot in pursuance of their duties, much of it drinkable.
Occasionally a ship full of privateers would decide they’d rather keep all the loot that they’d collected on behalf of their employers for themselves, and make a sort of freelance career of robbing and plundering. At which point they became officially known as pirates, with the rum, the booty, the tricorn hats, the yo-ho-ho, peg legs, eye patches, and other accoutrement.
Of course rum drinking wasn’t limited to privateers and pirates. Because rum was as good as cash, both cargo and military ships would often pay their crews with it. Eventually rum wages became rum rations, a sort of fighting sailor’s fringe benefit. American and especially British navies became famous for their rum rations, which started to go out of style when naval commanders decided that it might be better if the sailors operating their ships were sober, back in 1970.