The article attempts to study the obsolete Buddhist vocabulary of the Kalmyk language with evidence from the “early” 18th-19th century texts that have been introduced into the database of the Kalmyk National Corpus. As is known, within any language one can constantly witness two reciprocal processes: disappearance of some lexemes that pass out of use — and appearance of new ones. In terms of the historical approach to the studies of a word, the stages as follows can be distinguished: appearance of a lexeme, loss of novelty and movement into the realm of neutral lexis, appearance of obsolete features, passing out of use and designation as obsolete. But the process can be both slow, continuous — and uneven like, e.g., the case of religious lexis. Once shifted towards passive positions, such vocabulary did not disappear altogether but kept existing in corresponding texts. However, at certain historic moments obsolete vocabulary can get re-actualized and start functioning actively in speech; thus, re-emergence of a once obsolete word to active use is always a new stage in the life-cycle of the word. So, e.g., due to the social and political transformations that occurred in the past 20 years, religious terms and notions that used to be designated as obsolete are re-introduced into the active vocabulary. Kalmyk written monuments contain a huge layer of Buddhist lexis and expressions that passed out of active use and are difficult to understand (or cannot be understood at all) for contemporary Kalmyk speakers. Analyses of old written texts allow to fill some gaps relating to the vocabulary of modern Kalmyk and Mongolian languages in general. In view of the aforesaid, to enrich the contemporary vocabulary certain archaisms and obsolete words should be re-introduced – with due account of corresponding examples since the boundaries between the active and passive vocabulary (including mainly obsolete words) are not fixed. The considered examples testify that due to external reasons (both linguistic and extra-linguistic ones, i.e. those that resulted from social and political transformations) there occurred substitution of notions, restriction of meanings of words and other processes in modern Kalmyk which signifi cantly impoverish the vocabulary of the language. E.g., the word ӓӓldkhl expresses both the meanings of ‘report’ and ‘predestination’, bishilγkh stands only for ‘to contemplate’. It is the social movement for restoration of once lost spiritual traditions, cultural values and realities that stimulates the reintroduction of rare and obsolete lexis. The value of most of the words is indisputable since those constitute a huge layer of the culture and traditional national identity.