What about the one that was invented for Hayes heliport, north of Heathrow?
There were regular test/demo flights in/out and we got fed up with writing Hayes all the time so "invented" EGHZ. As you only used the last 2 letters if it started EG when writing on strips it was quicker. Why EGHZ? Well when the met came through it used to say Vis 2000m HZ (Haze - geddit) You won't find it anywhere official mind.