The Deplorable Word, as used by author C. S. Lewis in The Chronicles of Narnia, is a fictional magical curse which ends all life on a world except that of the one who speaks it.
In The Magician's Nephew, the children who are the central characters, Digory Kirke and Polly Plummer, come to a lifeless world called Charn.
Lewis does not explicitly link the Deplorable Word to any specific weapon of mass destruction, but he alludes to the power of humanity to destroy life.
[3] Near the end of the story Lewis has the lion Aslan say to the central characters from the Victorian era: It is not certain that some wicked one of your race will not find out a secret as evil as the Deplorable Word and use it to destroy all living things.
And soon, very soon, before you are an old man and an old woman, great nations of your world will be ruled by tyrants who care no more for joy and justice and mercy than the Empress Jadis.