As late as the turn of the 20th century, the Tat constituted about 11% of the population of the entire eastern half of Azerbaijan (see Baku Governorate, the section on Demography).

The 1886–1892 Tsarist population figures counted 124,683 Tats in the Russian Caucasus of which 118,165 were located in the Baku Governorate and 3,609 in the Dagestan Oblast.

[8] Arthur Tsutsiev notes that a major portion of Tats in the 1926 census were listed under the categories "Persians" and "Azerbaijani Turks".

[11] Archaeological material uncovered in present-day Azerbaijan, Armenia and Georgia include Achaemenid architecture, jewelry and ceramics.

Likely the ancestors of modern Tats settled in South Caucasus when the Sassanid Empire from the 3rd to 7th centuries built cities and founded military garrisons to strengthen their positions in this region.

[13] Khosrow I (531–579) presented the title of regent of Shirvan in eastern South Caucasus to a close relative of his, who later became a progenitor of the first Shirvanshah dynasty (about 510 – 1538).

Apparently, in this period the Turkic exonym Tat or Tati, which designated settled farmers, was assigned to the South Caucasian dialect of the Persian language.

By doing this, the Russian government helped to create and spread a new Turkic identity that, in contrast to the previous one, was founded on secular principles, particularly the shared language.

As a result, many Iranian-speaking residents of the future Azerbaijan Republic at the time either started hiding their Iranian ancestry or underwent progressive assimilation.

[18] According to the 19th-century Golestan-e-Eram, written by Abbasqulu Bakikhanov, Tati was widespread in many areas of Shamakhi, Baku, Darband and Guba:[19] “There are eight villages in Tabarsaran which are: Jalqan, Rukan, Maqatir, Kamakh, Ridiyan, Homeydi, Mata'i, and Bilhadi.

it becomes apparent from this that they originate from Fars.“According to the 1894 publication of the Caucasian Calendar, there were 124,693 Tats in the Caucasus,[21] however, due to the gradual spread of the Azerbaijani language, Tati was falling out of use.

[24] Although the majority of the Tat population of Azerbaijan and southern Dagestan uses the Turkic exonym Tati or Tat as a self-designation, there remain some local self-designations:[25] On December 14, 1990, the Azeri cultural and educational society for studying and development of Tati language, history, and ethnography was founded by the board of the Ministry of Justice of the Azerbaijan SSR.

The Persian settlers of the South Caucasus have long interacted with the surrounding ethnic groups, exchanging elements of their cultures.

While studying the works of Persian medieval poets of South Caucasus like Khaqani and Nizami Ganjavi some distinctive features of the Tat language have been revealed.

The traditional one or two-storeyed houses made of rectangular limestone blocks or river shingles and also have blank walls facing the street.

In his work Caucasian Jews-Mountaineers he came to the conclusion that the Mountain Jews were representatives of the Iranian family of the Tats, which had adopted Judaism in Iran and later moved to the South Caucasus.

This caused the whole cultural heritage (literature, theatre, music) created by Mountain Jews during the Soviet period to be attributed to the Tats.

Comparing physic-anthropological characteristics of Tats and Mountain Jews together with information about their languages suggests no signs of ethnic unity between these two nations.

The loanwords from Aramaic and Hebrew in Juhuri include words not directly connected with Judaic rituals (e.g. zoft resin, nokumi envy, ghuf body, keton linen, etc.)

Kurdov carried out measurements of a large group of Tat population of Lahij village and revealed fundamental differences[32] of their physical-anthropological type from the Mountain Jews.

[34] Speakers of Mountain-Jew dialect and Tati language are representatives of two different nations, each with its own religion, ethnic consciousness, self-designation, way of life, material and spiritual values.

Starting from the Middle Ages, the term Tati was used not only for the Caucasus but also for northern Iran, where it was extended to almost all of the local Iranian languages except Persian and Kurdish.