A demon or entity from the magical experiments and angelic of John Dee and Edward Kelly, explored further and popularised by Aleister Crowley and Victor Neuberg. Choronzon gained particular prominence in post modern magical traditions such as Chaos Magic.
John Dee refers to the entity Coronzom in his his private journals, but his magical system was first popularised in the book 'A True and Faithful Relation of What Passed for Many Years between Dr. John Dee ...and Some Spirits' published by Meric Casaubon. Casaubon introduced the variant spelling Coronzon, replacing the 'm' with an 'n'. Possibly this happened as a result of misreading Dee's manuscript or sloppy transcription. The spelling with 'Ch' instead of 'C' comes from the work of Crowley, who apparently added the extra letter in order cause the name to add up to the number 333 in his prefered system of numerology.