Since around 1750, Davy Jones's Locker has been an idiom for the bottom of the sea; the resting place of drowned sailors. It seems that this age-old phrase has many possible origins.

In The Adventures of Peregrine Pickle (1751), Tobias Smollett wrote: "I'll be damned if it was not Davy Jones himself. I know him by his saucer eyes, his three rows of teeth and tail, and the blue smoke that came out of his nostrils." This same Davy Jones, according to the mythology of sailors, is the fiend that presides over all of the evil spirits of the deep; and is often seen in various shapes, perched atop the rigging on the eve of hurricanes, shipwrecks, and other disasters, to warn of death and woe.

The original Davy Jones may have been the 16th-century owner of an English pub, commemorated in the ballad "Jones Ale is Newe,"who stored his ale in a mysterious locker and was reported to be feared seamen. Or Jones could be a corruption of Jonah, the unlucky biblical character swallowed by a whale, and Davy the Anglicization of the West Indian word duppy, meaning "a malevolent ghost or devil." A third, more plausible explanation proposes the Jonah above for Jones, but derives Davy from St. David, the patron saint of Wales, often invoked by Welsh sailors. Jonah was considered bad luck to the sailors aboard the vessel on which he was "attempting to flee God's wrath" and the phrase was first recorded in Captain Francis Grose's Classical Dictionary of the Vulgar Tongue (1785) as David Jones' Locker, which lends more support to the Welsh patron saint theory.

The locker phrase probably refers to an ordinary seaman's chest, not the old pub owner's mysterious locker.