Both languages were once spoken in the Tarim Basin in Central Asia, now the Xinjiang province of China. The speakers of these languages have been identified with the 'Tocharians' mentioned in Greek sources. The name "Tocharian" itself is speculative. Chinese records of the time also mention this group, as nomadic 'barbarians'.
Tocharian is documented in manuscript fragments, mostly from the 7th and 8th centuries CE (with a few earlier ones) that were written on palm leaves, wooden tablets and Chinese paper, which had been preserved by the extremely dry climate of the Tarim Basin. The language was already old enough by the 6th century to have split into the two dialects, or separate languages, that are preserved in the manuscripts.
The existence of the Tocharian languages and alphabet was not even guessed at, until chance discoveries in the early 20th century brought to light fragments of manuscripts in a then unknown alphabetic syllabary that proved, astonishingly, to be in a hitherto unknown branch of the Indo-European family of languages, which has been named 'Tocharian'. The alphabet they were using is derived from the North Indian Brahmi alphabetic syllabary. They wrote on palm leaves, Chinese paper, and wooden tablets. It soon became apparent that a large proportion of the manuscripts were translations of known Buddhist works in Sanskrit and some of them were even bilingual, thus providing a kind of Rosetta stone that has facilitated decipherment of the new language. The bulk of the texts were dated from the seventh and eighth centuries. Besides the Buddhist and Manichaen religious texts, there were also monastery correspondence and accounts, commercial documents, caravan permits, and medical and magical texts. Many Tocharians embraced Manichaean duality or Buddhism.
Tocharian has upset some theories about the relations of Indo-European languages and is revitalizing linguistic studies. The Tocharian languages are a major geographic exception to the usual pattern of Indo-European branches, being the only one that spread directly east from the theoretical Indo-European starting point in southern Russia.
Tocharian was the language of the short-lived, yet influential Kushan empire. Tocharian probably died out under Uighur rule of modern Xinjiang. They mixed with the Uighurs to produce much of the modern population of Xinjiang.
See also: Language families and languages