"Was there a real Davey Jones? That's a question linguists have pondered since 18th-century sailors started using the name for the evil spirit of the sea or the deadly depths of the ocean. Some claim the original Davey Jones was a British pirate, but there's no evidence such a person actually existed. Others swear he was a London pub owner who kept drugged ale in a special locker, served it to the unwary, then had them shanghaied to sea. But the theory considered most plausible is that the "Davey" in "Davey Jones' Locker" was inspired by St. David, the patron saint of Wales, who was often invoked by Welsh sailors. The "Jones" is traced to Jonah, the Biblical figure who was swallowed by a whale."
-- Merriam-Webster Inc., http://www.m-w.com