*Late Latin, probably of Oriental origin but influenced by Latin daemon plus Gorgo "Gorgon". (WNWD2nd) Webster's New World Dictionary 2nd College edition, 1986.
* Late Latin Demogorgon from the Greek for people plus grim, terrible, whence Gorgon, but of uncertain origin. The idea of Demogorgon being a corrupted form of demiurge is highly doubtful. Medieval writers connected it with "demon" meaning either "terror to demons" or "terrible demon". From its connection with magic, it may be a disguised form of an Oriental name.  The Oxford English Dictionary Vol. III D-E. Reprint 1961, 1933 first ed..
*Late Latin Demogorgo, from Greek daimon "demon" plus gorgos"grim, dreadful". (WN20CD)

    Demogorgon was the name of an ancient deity, a primeval creator god, who was known previous to the gods of Greek mythology, possibly of Oriental origin. He is also referred to as a spirit and as a demon, never as a mortal being. The Greeks passed the story to the Romans which was recorded by the monks, so the story shifted with each re-telling, yet even in Medieval writings he is referred to as a primeval creator. All other gods are said to have come from him. He is sometimes said to have commanded the spirits of the Netherworld, or to have been of the Netherworld himself. He is also said to have lived in the Himalayas, and every five years required an accounting from his subjects of the spirit world concerning their stewardship of the world. He inspired awe and even fear, and was part of alchemical and probably other rites. Whether he was evil or good is not agreed.
    His name was not to be spoken, and some feared that the speaking would cause catastrophe and death.
    In the 4th century around 450 AD, a Christian writer, a Scholiast, Lactantius or Lutatius Placidus, broke with tradition by actually writing the name down in Statius's Theb.IV.516. He wrote it as the name of the great nether deity invoked in magic rites.
    Lucan's Pharsalia VI.742 is a slightly later reference, in which Rowe (a Scholiast:), describing the Demogorgon, says:

"Must I call your master to my aid,
At whose dread name the trembling Furies quake,
Hell stands abashed, and earth's foundations shake?"
   A Byzantine going by the alias of Pronapides, Athenian states that all gods are descended from Demogorgon.
    Theodontius wrote between the 9th and 11th centuries, probably a philosopher of Campanian origin. He picked up the belief that all gods were descendents of Demogorgon from Pronapides. Theodontius also came up with a very mixed traditon including the Olympic pantheon, syncrestic mythology, cosmogonic speculations of Greek philosophers, and comments from a Greek historian of the 4th century BC (probably Lactantius with a typo making the BC).
    Conrad de Mure's Repertorium in 1273 AD describes Demogorgon as the primordial god of ancient mythology.
    This same descriptions as in the Repertorium and in Theodontius's writings are in Boccaccio's Geneology Deorum (Geneology of the Gods), which appears to be the source of the word in the "modern' literature of Ariosto, Spenser, Marlowe, Dryden, Milton, Shelley, Giraldi, Chapman, Burton, and others. He started the work in the middle of the 14th century and spent his last twenty-five years of life on it. It was done at the request of Hugues IV, King of Cyprus. Boccaccio picked up the name from Theodontius, but with a grammatical error. Demogorgon is presented as founder of the whole race of gods, but is unheard of by classical antiquity. Seznec says, "Demogorgon is a grammatical error, become god."

    Quotes mentioning the Demogorgon's supposed traits follow:
    1590 Spenser Faerie Queen.IV.22: "O thou (Night) most auncient Grandmother of all... Which wast begot in Daemogorgon's hall."
    Faerie Queen, continued: IV,ii,47: says that the Demogorgon dwells "down in the bottom of the deep abyss with the three fatal sisters."
    1667 Milton P.L.Paradise Lost.II.965, 966: "And by them stood Orcus and Ades, and the dreaded name of Demogorgon."
    Ariosto: "Demogorgon was king of the elves and fays who lived on the Himalayas, and once in five years summoned all his subjects before him to give an account of their stewardship."
    1681 Dryden Sp.Friar.V: "He's the first begotten of Beelzebub, with a face as terrible as Demogorgon."
    1705 Purshall Mech. Macrocosm 85: "The saline and sulphurous vapors, I take to be the true Demogorgon of the philosophers, or grandfather of all the heathen gods, i.e. metals."
    1821 Shelley Prometheus Unbound I.207: "All the powers of nameless worlds...and Demogorgon, a tremendous gloom."
Demogorgon appears as the eternal principle that ousts false gods.
    1850 Keightley Fairy Mythol. 452: "According to Ariosto, Demogorgon has a splendid temple palace in the Himalaya mountains, whither every fifth year the Fates are all summoned to appear before him, and give an acount of their actions."
    Dryden The Flower and the Leaf, 493: he appears as "cruel Demogorgon".

    Popular in literature, poetry, magic, and alchemy, Demogorgon is also depicted in a number of paintings as mixed as the texts. One artist showed Demogorgon as an old man in his cavern along with other characters including Greek and Assyrian.

Webster's New World Dictionary 2nd College edition, 1986
The Oxford English Dictionary Vol. III D-E. Reprint 1961
Webster's New 20th Century Dictionary Unabridged 2nd edition, c 1983
Merriam Webster's Collegiate Dictionary, 10th edition, 1993
Webster's Seventh New Collegiate Dictionary.  1970.
The American Heritage Dictionary, 2nd College edition. 1982
The Random House Dictionary of the English Language Unabridged. 1966
Brewer's Dictionary of Phrase and Fable. ed Ivor H. Evans. Harper & Row, pub. 1981
The Survival of the Pagan Gods. Seznec.