The article presents a part of the research on the Russian and Polish lexical units containing the глуп-/głup- root. The noun, verb and adverb forms have been analysed from the point of view of their meanings and the functional, stylistic and derivational properties. That is why the research material includes the contemporary units such as colloquialisms and lexemes of the restricted usage (archaisms and linguistic variants) which occur in both languages. The lexical units have been selected from the contemporary and historical explanatory and etymological dictionaries as well as from the former and dialectal lexis.

The article deals with the Russian and Polish phraseologisms including some proverbs and sayings describing madness and the lack of mind. The material has been presented with regard to dominating imaginations of madness and stupidity being displayed in the semantics of examined units. These units include – hitting, aside movement, the lack of sensitivity to outer stimuli, the fragmentation of entirety, lack of components, etc.

The article presents the context‑determinated meanings of the дурак (durak) lexem based upon the satirical sketches Well‑Meant Speeches by Mikhail Saltykov‑Shchedrin. At the beginning is the etymology of the word and then general vocabulary definitions produce four basic meanings for the word: 1. a good and honest man; 2. a person being the object of widely‑spread mockery and jibes; 3. a person unable to behave in a proper way; 4. a person unable to administer their property in a good way as well as not to live their life successfully – a lame duck, a sluggard and a drunkard. From amongst those meanings the author tries to notice the mutual parallels which interpret visions of the fool in Saltykov‑Shchedrin’s sketches as well as the contemporary vision of the Russian mentality and its folk tradition.