A lock which has no spring catch. Metaphorically, a state of things so entangled that there seems to be no practical solution.
“Things are at a dead-lock.” —The Times.
Dead Men Empty bottles. Down among the dead men let me lie. Let me get so intoxicated as to slip from my chair, and lie under the table with the empty bottles. The expression is a witticism on the word spirit. Spirit means life, and also alcohol (the spirit of full bottles); when the spirit is out the man is dead, and when the bottle is empty its spirit is departed. Also, a loaf of bread smuggled into the basket for the private use of the person who carries the bread out is called a “dead man.”
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894