Both Uses of

abyss

in

The Epic of Gilgamesh

These are the measurements of the barque as you shall build her: let her beam equal her length, let her deck be roofed like the vault that covers the abyss; then take up into the; boat the seed of all living creatures.†
Book 5 *

abyss = a hole or dropoff so deep the bottom cannot be seen -- often used figuratively to imply a frightening bottomless pit

Then the gods of the abyss rose up; Nergal pulled out the dams of the nether waters, Ninurta the war-lord threw down the dykes, and the seven judges of hell, the Annunaki, raised their torches, lighting the land with their livid flame.†
Book 5