Davy Jones' locker
The bottom of the sea; the resting place of drowned mariners.
Davy Jones is the evil spirit of the sea. There are various possible attempts to explain the name by associating it with someone of a similar name:
Jones may be a corruption of name of the biblical seaman Jonah. Jonah denoted bad luck on to seamen.
Davy Jones was a 16th century publican who imprisoned drunken sailors in a locker and press-ganged them to serve on ships.
The name comes from the patron saint of sailors - St. David.
None of these is supported by any evidence - they are little more than guesses.
The first source of the use of the name comes from Tobias Smollett's The Adventures of Peregrine Pickle 1751:
"'By the Lord! Jack, you may say what you wool; but I'll be damned if it was not Davy Jones himself. I know him by his saucer eyes, his three rows of teeth, his horns and tail, and the blue smoke that came out of his nostrils. What does the blackguard hell's baby want with me? I'm sure I never committed murder, except in the way of my profession, nor wronged any man whatsomever since I first went to sea.' This same Davy Jones, according to the mythology of sailors, is the fiend that presides over all the evil spirits of the deep, and is often seen in various shapes, perching among the rigging on the eve of hurricanes, shipwrecks, and other disasters, to which a seafaring life is exposed; warning the devoted wretch of death and woe."
The first source that mentions Jones' locker is the 1803 Naval Chronicle:
"...seamen would have met a watery grave; or, to use a seaman's phrase, gone to Davy Jones's locker."