Tehom (Hebrew: תְּהוֹם), literally the Deep or Abyss (Greek Septuagint: ábyssos), refers to the Great Deep of the primordial waters of creation in the Bible. Tehom is a cognate of the Akkadian word tamtu and Ugaritic t-h-m which have similar meaning. As such it was equated with the earlier Sumerian Tiamat.
Tehom is first mentioned in Genesis 1:2, where it is translated as "deep" below:
And the earth was without form, and void; and darkness was upon the face of the deep. And the Spirit of God moved upon the face of the waters.
It was from here that the waters of Noah's flood had their origin and the place that God temporarily receded the Red Sea for the Israelites to pass over  before destroying the pursuing Egyptian army, and the place that God will dry up for the righteous to walk on towards their redemption at the End of Days (Isaiah 11:15, context entire ch. 11).
Gnostics used this text to propose that the original creator god, called the "Pléroma" or "Bythós" (from the Greek, meaning "Deep") pre-existed Elohim, and gave rise to such later divinities and spirits by way of emanations, progressively more distant and removed from the original form.
Assyriologist Heinrich Zimmern writes in his comparative study of Babylonian and Hebrew creation myths:
According to both traditions before the creation all was water. The deep is personified as a terrible monster, which in the Babylonian version bears the name of "Tihamat," corresponding to the Hebrew "Tehom," used as the technical expression for the primæval ocean. The Hebrew word is employed without the article, like a proper name, thus indicating that in Israelite tradition also it stood originally for some mythological being.
- Gen. 7:11 "In the six hundredth year of Noah's life, in the second month, the seventeenth day of the month, the same day were all the fountains of the great deep broken up, and the windows of heaven were opened
- (Isaiah 51:10) [Art] thou not it which hath dried the sea, the waters of the great deep; that hath made the depths of the sea a way for the ransomed to pass over?
- Heinrich Zimmern, The Ancient East, No. III: The Babylonian and Hebrew Genesis; translated by J. Hutchison; London: David Nutt, 57–59 Long Acre, 1901.
- Stieglitz, Robert R. (1990). "Ebla and the Gods of Canaan". In Cyrus Herzl Gordon; Gary Rendsburg. Eblaitica: essays on the Ebla archives and Eblaite language. Eisenbrauns. pp. 79–90 (p.88). ISBN 978-0-931464-49-2.