Tabiti is not a supreme God, which is Tengri, but a Primogenitor Goddess known in the matriarchal religions as Great Mother, Astarte, Ashtoreth, Ishtar, Cybele and a number of other local names. She created the world, She is a virgin, She is not a part of a couple, or an accessory to another Deity.

Per the Rafael Bezertinov work "Tengrianizm – Religion Of Türks And Mongols", the Heavenly Hierarchy starts with Tengri and his consort Umay, who are exact equivalents of the Greek Uranus and Gaia, but without a legacy of bloody and adulterous adventures. As a Primogenitor Goddess, Tabiti is superior and preeminent to Tengri. In the Greek and Roman worlds, she was reduced to a household Goddess under the names of Hestia and Vesta.

With the paucity of information on Tabiti, and because Herodotus is the only source with no corroborating or alternate account, all etymological suggestions for Tabiti are pure speculations. Some etymologies, in order of likelihood, are these:

Tabiti from the Türkic word Ebi or Ebe engender, birth-giving woman, which produced a Türkic name Umay (b/m alternation), a perfect semantical equivalent as a Supreme Mother, "Engender". In semantical cluster, Ebi/Ebe contains "grandmother" (a perfect complement for Türkic and Scythic Babai/Papai  "grandfather"), "tribe", a derivative "midwife", "dear woman". Tabiti/Ebe is a perfect match for the Biblical Eve, a proper Türkic complement for the Türkic Adam "man". Ebi/Eve and Adam came to the Hebrew Bible through a long chain of Sumerian, Acadian and Assyrian. In Slavic languages, Ebi/Ebe retained its direct Türko-Slavic verbal meaning "to fuck", and is a most popular word in the Russian verbal lexicon. To derive the Slavic verb  ebat/ibat from the ancient Hebrew hawwah "creature, living being", suggested as a pra-form of the Biblical Eve, is preposterous; on the other hand, to derive the Hebrew hawwah "creature, living being" fgrom the Biblical Eve is quite possible, both these words, Adam and Eve, became common nouns ling before formalization of the Bible in the 5th c. BC (I.Durmush, 2002, Scythians//The Turks, Ankara).

Tabiti from the Türkic word tap, tabynu "worship (v)", corroborated by Etruscan than (pronounced t-han - Translator's Note), to beseech with the Etruscan version of the God(dess) Tabiti. This version does not contradict the Turkic Ebi "woman in labor", but complements the semantic field as "adoration" supplements the "Adonis" and "Adonai", with many similar examples. (Adile Ayda, 1992, Etrüskler (Tursakalar) Türk idiler. Ankara)

Tabiti from the Türkic Chuvash word tupa "oath" and "to speak". Applying free-flying imagination, you can ascribe any semantical extension, like the "who has given the vow of chastity". A better semantical example would be connected with a derivative "adore, adoration", a cognate of Greek Adonis, from Semitic Adon "lord", "ruler", a verb form "to judge, rule" (V.Stetsyuk, Research on Prehistoric Ethnogenetic Processes in Eastern Europe, Lvov, 2003)

Tabiti is a Goddess of the home hearth, in Greek Gestia, in Scythian apparently from the Türkic word tabu ‘find, swindle’ (M.Zakiev, 1995).

Herodotus' description of Tabiti:

 [4.59] They worship only... Tabiti (Roman Vesta, Greek Hestia, "Vesta" is used in Herodotus' translations), whom they reverence beyond all the rest... In the Scythic tongue Vesta is called Tabiti

[4.127] ...Idanthyrsus, the Scythian king, replied: ...As for the Lords, I acknowledge only Papaeus (English Jove, Roman Jupiter, Greek Zeus, "Jove" is used in Herodotus' translations) my ancestor, and Tabiti (Roman Vesta, Greek Hestia, "Vesta" is used in Herodotus' translations) the Scythian queen. Yer (English Earth, German Erde, from the Türkic root "er," which produced Germanic noun "ertho," and ultimately German "erde," Dutch "aarde," Danish and Swedish "jord," and English "earth." Related forms include Greek "eraze," meaning "on the ground," and Welsh "erw," meaning "field". "Earth" is used in Herodotus' translations) and Su ("Water" is used in Herodotus' translations. Yer-Su or Yer-Sub is a undivided Goddess presenting the surrounding world and encompassing the lands and the waters of the world, in opposition to the Sky - Tengri. The Herodotus' translation substituting "Yer and Sub, Earth and Water" for "Yer-Sub, Earth-Water", separates a unitary Deity into two independent Deities, changing the semantics of the Idanthyrsus' statement),...