Admiral Benbow was a national hero, and plenty of real pubs were named after him as well as fictional ones. I don't find that surprising at all. Stevenson published Treasure Island in 1883, some 180 years after Benbow's death. The songs are at the very least a century older than the novel. There is plenty of information earlier in this thread; though, as is inevitably the way with combined threads, that information may not appear in the most helpful order.