The history of grog is pretty interesting. This section of the wikipedia article was pulled almost wholecloth from The Sea Rover's Practice, which is a great book, if a bit dry.
British sailors came to be called limeys because the citrus juice of choice was lemons, until inconvenient political alliances limited access to the fruit, and the Brits switched to limes.
Edit: Sadly, the URL encoding doesn't seem to work. Sorry =(