 Tocharian A and B are not mutually intelligible.Properly speaking, based on the tentative interpretation of "twqry" as related to "Tokharoi", only Tocharian A may be referred to as "Tocharian", while Tocharian B could be called "Kuchean" (its native name may have been "kuśiññe"), but since their grammars are usually treated together in scholarly works, the terms A and B have proven useful.A common Proto-Tocharian language must precede the attested languages by several centuries, probably dating to the 1st millennium BC.