A BRIEF HISTORY OF RUM
Rum was discovered as sugar growers cured sugar in clay pots, and as it crystallised, a brown liquid called molasses drained out of the remaining sucrose. This was recycled by natural fermentation, and then by distillation to give a clear liquid, which darkened as it matured in wooden casks.
The French called it 'tafia' and the English rum-bullion - shortened to rum. Perhaps the term originated because it was 'rum' (odd) to get precious booty (bullion or alcohol) out of waste products.
Fresh water, even in casks, would not keep for long on board ships and from early times wine or beer was then substituted. Shortage of stowage space for beer led to the introduction of brandy at sea, then rum in the 18th century after the capture of Jamaica.
Rum was cheap and plentiful in the Caribbean because it was easily made from sugar cane. It was issued twice a day, at lunch and at supper, the daily ration being a pint of rum per man and half a pint for a boy.
Rum was also dished out regularly upon pirate ships, following the Royal Navy tradition who perhaps didn't keep to their daily limit and pirates were often drunk (Captain Jack Sparrow style) because there was little alternative liquid to drink.