ACCORDING to Michael Quinion of World Wide Words, the earliest mention of Davy Jones was in a book, The Adventures of Peregrine Pickle which was written by one Tobias Smollett all the way back in 1751. There is no concrete evidence that the villainous Davy Jones really existed, of what his origins were or how the reference to his locker came to be (other than being sent there would surely mean a watery grave).  

So for the most part Davy Jones is a creature of folklore, like the unicorn and King Arthur. Anything to the contrary is purely guesswork.