Wayne Horowitz discusses the earth/underworld being a place of no return in Mesopotamian cosmology.
Wayne Horowitz, Mesopotamian Cosmic Geography (Winona Lake, Indiana.: Eisenbrauns, 1998), 268, 272
Sumerian Names Akkadian names
. . .
ki erṣet la târi ‘Earth of No Return’
. . .
ki. Sumerian ki occurs countless times in the cosmic pair an.ki ‘heaven and earth’ and in parallelisms between heaven and earth in texts such as Gilgameš and the Ḫuluppu-Tree, Enik and Ninmaḫ and KAR 4, where an an ki are separated from one another in early times (see pp. 134-42). As such, ki also occurs as a name for the exposed upper surface of earth, the earth’s surface.
Two examples of ki = erṣetu as the underworld occur in bilingual texts. In SBH 139 no. iv 157-58, 600 Anunnaki are placed in ki = erṣetu (see p. 18). These 600 can be identified as the 600 Anunnaki of the underworld in KAR 307.37. In Utukku Lemnutu XVI, demons are sent down to ki = erṣetu from the earth’s surface:
udug.ḫul a.lá ḫul ki.šè ḫa.ba.e11.dè
ú-tuk-ku lem-nu a-lu-ú lem-nu ana erṣetimtim li-ri-du
CT 12 22: 280-281 + duplicates
(cf. O. Gurney, AAA 22 86: 126-137)
Let the evil utukku-demon and evil alû-demon go down to the underworld.