A bilingual Sanskrit/Tocharian B manuscript from the Petrovsky collection (SI P/65b1), kept in St. Petersburg, contains the line tokharika : kucaññe iscake. This text has been repeatedly adduced as a testimony for the name of the Tocharian language: Skt. tokharikahas been connected with Tukhāra, Toch. B kucaññe being understood as ``Kuchean'', despite various difficulties. The actual adjective meaning ``Kuchean'' is Toch. B kuśiññe, the form of which is not compatible with kucaññe. Starting from an examination of the original manuscript, a totally new interpretation of the line is proposed: the word tokharikareflects a Prakritic form of Gāndhārī type, and conceals two homonymous Sanskrit words of the Indian lexicographical tradition, to wit tūbarikah ``eunuch'' and tūbarikā ``fragrant earth''. Those words are actually translated by Toch. B kucaññe and iscake, respectively, the meaning of which can be established by independent evidence. Toch. A kucim, which is the perfect formal match of B kucaññe, is used as a derogatory term: ``unmanly, impotent'', or the like. Toch. B iscake is related to iścem ``clay'' in the same language, and refers to ``a kind of clay''. Furthermore, it shows important and far-reaching connections with several words of the same technical field in Indo-Iranian and in other languages of Central Asia.