The article focuses on the semantics as the main factor motivating the author’s transformations of idioms (fi xed constructions). At the beginning of the article, we propose a tentative defi nition a of the author’s idiom transformation, which is to be used for further reasoning. Then, we analyze the main principles of classifi cation of author’s phraseological units by various scholars, and, this done, the assumption is made that the main motivator of these transformations should be semantics, since any formal transformation of a phraseological unit as a fi xed word combination, possessing opaque but to a certain extent deducible meaning, inevitably aff ects its meaning. The principal feature of the author’s transformation is that the author uses an idiom not just as a ready-made construction, but reinvents it, adapting it to the specific situation he/she describes. Thus, all such transformations can be represented as an individual intention of the author to resist “fi xedness” in the language constructions by rethinking them: in other words, such transformations aim not only to formally “decorate” the text or be used in language game (as in the case of advertising or propaganda texts), but as an artistic device allowing the author to refl ect on the described events through experiments with language. As an illustration of the presented theses, a number of examples of the author’s rethinking of phraseological units by F. M. Dostoevsky and other authors are analyzed and commented.