The article is devoted a phenomenon well known to researchers of the naïve / mythological view of the world – semantic syncretism (inseparability) of terms denoting diseases and entities of evil. This phenomenon is rooted in the system of traditional beliefs according to which disease is personified and thus can act on its own accord as some sort of a malignant being – a demon or a disease-spreading spirit, and not just a «collection of symptoms». This is especially evident in the genre of curses: linguistic and pragmatic features of such texts make it difficult to distinguish between the entities behind the names of malignant characters. Names of maladies and demons mentioned in curses may be related to each other etymologically (there is a well-known semantic-motivational model in Slavic languages: ‘unclean forces’ → ‘disease’ and the reverse ‘disease’ → ‘unclean forces’), or they may have developed polysemy on a synchronic level, without genetic ties. Besides, the situation of false polysemy is quite typical for the genre of curses: a malignant character is usually demonized (both by the bearers of folk tradition and by text interpreters, including lexicographers) even when in practice the corresponding word refers to an inanimate object (a disease, a tool) or does not exist at all (e.g. some curses mention a certain ‘boday’ entity, supposedly an evil spirit, which in fact originates from the phrase ‘bog day’ [=god give]).