Once upon a time a glitch fell through an imagined hole in the first floor. Mind, the bottom floor has not been imagined then yet! But the merciful and glorious Tii came up with this floor, so that to stop the falling glitch's fall. It worked, as we can see in this testimonial. :)

And then Hell's bartender decided to get ritch so he strarted to make holes all over the Ur in hope to find oil. That's how we got 7th and deepest circle of hell and bottom of all bottoms.
Today glitchens use so called "wine of dead" which is filled with oil to remove their resources. :p