While there is no concrete answer, there are several plausible origins of this term. In an old factory, where smoke and dust were everywhere, a 2100° opening would have created an illusion not unlike that seen in paintings of saints and angels where “The Glory” radiated from their heads. A break in the clouds where sunlight passes through is also called a glory hole. However, the term has more recently fallen out of use and the term “Reheating Furnace” is more widely used.