Ghu is either a beetle living on Vulcan (no relation to Star Trek's Vulcan) or Wollheim personified – or possibly both, depending on who was defining it and when. Various members of the New York Futurians served as acolytes of Ghu, with fitting high-sounding church titles.
Ghu's holy color is purple because early fanzines were published using spirit duplicators or hectographs (typically referred-to in North America by the most popular brand name, "Ditto Machines"). Their master carbon typically used purple ink.
Prior to the advent of microcomputers, Ditto Machines were widely-used in churches, schools, and universities. Fans would often commandeer these machines to publish fanzines.
It was routine for purple ink to stain one's fingers while manipulating the machine. This led to such oaths as, "By Ghu's purple fingers," or, "By Ghu's Holy Purple Robes."
Ghu has approximately the same meaning and emotional impact as the American English word, "God."
Ghu sometimes appears in science fiction stories as an in-joke, used rather than "God" or a any specific name for God.
In one long-running in-gag, H. Beam Piper's Terro-Human Future History portrays Ghu as the Thoran grandfather god. Characters occasionally swear by Ghu but are careful not to do so while in the presence of a Thoran.
Well, take Ghu, the Thoran Grandfather-God. Ghu was as preposterous, theologically, as Merlin was technologically; Ghu, except to Thorans, was a Federation-wide joke. But he'd known a couple of Thorans at the University, funny little fellows, with faces like terriers, their bodies covered with matted black hair. They believed in Ghu the way he believed in the Second Law of Thermodynamics. Ghu was with them every moment of their lives. Take away their belief in Ghu, and they would have been lost and wretched.
- H. Beam Piper, The Cosmic Computer
Ghu's Lexicon was a short dictionary of fannish terms by Ralph M. Holland . It contained forty-four words and their meanings. Produced by the National Fantasy Fan Federation, it was distributed free to members of the club. It was 16 pages with dimensions of 4¼" X 5½".
In modern times, Ghu's Lexicon has been succeeded by Fancyclopedia 3 .