The spellings Bitu and Bidu are both used in modern scholarship. The name of the gatekeeper of the underworld was written in Sumerian as dNE.TI. In older sources, it was read as Neti. The reading Bidu has been established by Antoine Cavigneaux and Farouk al-Rawi in 1982 based on the parallel with the syllabic spelling Bitu (bi-tu). Multiple other syllabic spellings are attested, including bí-ti, bí-du8, bí-duḫ and bi-ṭu-ḫi. Michael P. Streck suggests that the forms with du8 should be understood as a learned spelling based on the meaning of this cuneiform sign, "to loosen," and on the Sumerian word for a gatekeeper, ì-du8. The name is however derived from the imperative form of Akkadian petû, "open." Based on this etymology Dina Katz argues that the concept of a gate of the underworld, and the descriptions of this location in which it resembles a fortified city, were Akkadian in origin.
In the so-called First Elegy of the Pushkin Museum Bitu's name is written without a dingir sign denoting divinity, though he is classified as a deity in Death of Gilgamesh and elsewhere. The omission might therefore be a simple scribal mistake.
Bitu's primary function is that of a gatekeeper (ì-du8). He could also be addressed as the "great gatekeeper," ì-du8 gal. This epithet was transcribed in Akkadian as idugallu. In incantations which were meant to compel demons and ghosts to return to the underworld, a formula placing them under the control of Bitu was sometimes used.
His position in enumerations of underworld deities varies between sources. The First Elegy of the Pushkin Museum pairs him with the legendary king Etana, also believed to be a functionary of the underworld. In an incantation from the middle of the second millennium BCE, he appears between Namtar and Gilgamesh. An Assyrian funerary inscriptions mentions him alongside Ningishzida.
In a single text, the position of the doorman of the underworld is instead assigned to Namtar.
In Inanna's Descent, Bitu announces the arrival of the eponymous goddess in the land of the dead to his mistress, Ereshkigal. He is also tasked with telling Inanna to remove various articles of clothing while she enters through the seven gates of the underworld. In the text Death of Ur-Namma, Bitu is absent, but seven anonymous doorkeepers are mentioned among the underworld deities, possibly as a reflection of the motif of seven gates mentioned in Inanna's Descent.
The late text Underworld Vision of an Assyrian Prince describes Bitu as a hybrid creature with the head of a lion, feet of a bird and hands of a human.
- Katz 2003, p. 401.
- George 2003, p. 128.
- Deller 1991, p. 14.
- Kramer 1961, p. 87.
- Streck 2014, p. 163.
- Nashef 1991, p. 67.
- Katz 2003, p. 174.
- Katz 2003, p. 175.
- Katz 2003, p. 120.
- Katz 2003, p. 376.
- Katz 2003, pp. 174–175.
- George 2003, p. 500.
- George 2003, p. 130.
- Deller 1991, pp. 14–15.
- Streck 2014, p. 164.
- Katz 2003, p. 179.
- Katz 2003, p. 358.
- Deller, Karlheinz (1991). "On the Names of some Divine Doorkeepers" (PDF). N.A.B.U. Nouvelles Assyriologiques Brèves et Utilitaires (1): 14–16. ISSN 0989-5671. Retrieved 2022-05-13.
- George, Andrew R. (2003). The Babylonian Gilgamesh epic: introduction, critical edition and cuneiform texts. Oxford New York: Oxford University Press. ISBN 0-19-814922-0. OCLC 51668477.
- Katz, Dina (2003). The Image of the Netherworld in the Sumerian Sources. Bethesda, MD: CDL Press. ISBN 1-883053-77-3. OCLC 51770219.
- Nashef, Khaled (1991). "A Further Note on the Name of the Chief Doorkeeper of the Netherworld" (PDF). N.A.B.U. Nouvelles Assyriologiques Brèves et Utilitaires (1): 67–69. ISSN 0989-5671. Retrieved 2022-05-13.
- Kramer, Samuel Noah (1961), Sumerian Mythology: A Study of Spiritual and Literary Achievement in the Third Millennium B.C.: Revised Edition, Philadelphia, Pennsylvania: University of Pennsylvania Press, ISBN 978-0-8122-1047-7
- Streck, Michael P. (2014), "Türhütergottheiten A. In Mesopotamien · Divine door-keepers A. In Mesopotamia", Reallexikon der Assyriologie, retrieved 2022-05-13