De Vermis Mysteriis, or Mysteries of the Worm, is a fictional grimoire created by Robert Bloch and incorporated by H. P. Lovecraft into the lore of the Cthulhu Mythos.
Creation
The tome first appears in Bloch's short story "The Shambler from the Stars" (1935), in which a character reads a passage from the book and accidentally summons an extradimensional horror.Bloch, then a teenager, corresponded with Lovecraft about the story prior to its publication, in part to get permission to kill off a character based on the older writer. While giving his enthusiastic blessing, Lovecraft also suggested that the book featured in the story, named by Bloch as Mysteries of the Worm, be referred to instead by the Latin equivalent De Vermis Mysteriis.Lovecraft also provided Bloch with a bit of Latin to use as an invocation from the book: "Tibi, magnum Innominandum, signa stellarum nigrarum et bufaniformis Sadoquae sigilim"--which can be translated as "To you, the great Not-to-Be-Named, signs of the
Source:
http://en.wikipedia.org/wiki/De Vermis Mysteriis