This article, based on representative corpus data, examines the non-trivial morphosyntactic properties of the experiential predicative vsë ravno (which, as we argue, emerged under Polish influence) in the Russian language from the 17th to the 21st centuries. While the semantic structure of this locution has been described in detail by Leonid Iomdin, its diachronic evolution and the morphosynthetic status of its components have rarely been addressed by linguists. It is shown that originally the elements vsë ‘everything’ and ravno ‘equal’ exhibited a high degree of morphosyntactic and prosodic autonomy (in particular, the set of linguistic units that could be inserted between them was remarkably broad), forming at the same time a semantically idiomatic complex. The contradiction between semantic cohesion and morphological autonomy was resolved in the history of Russian through the reduction of the morphosynthetic status of these elements and an increase in the morphological cohesion of the phrase vsë ravno. This process can be considered complete in the modern language for the construction P vsë ravno [čto/kak] Q meaning ‘P is equivalent/equal to Q’ and for the adverbial vsë ravno meaning ‘in any case; anyway’. However, in its original meaning (‘does not matter; no matter’), this unit shows signs of a secondary wordform with incomplete morphologization, especially under negation. In these latter contexts, it is still possible to insert a limited set of other units between vsë and ravno (primarily, the enclitic li and the subject dative forms of personal pronouns). Nevertheless, the tendency towards full morphological integration is clearly manifested even in negative contexts through the gradual “externalization” of these units into postposition: for example, the sequence ne vsë ravno li (+ dative) is particularly frequent in Russian poetry.