Mackey's Encyclopaedia of Freemasonry and its Kindred Sciences
A Hebrew word ab-ad-done, signifying destruction. By the Rabbis it is interpreted as the place of destruction, and is the second of the seven names given by them to the region of the dead. In the Apocalypse (Revelation ix, 11) it is rendered by the Greek word Apollyon, and means the destroyer. In this sense it is used as a significant word in the high degrees.