Enantiosemy describes a situation in which a lexical unit acquires opposing meanings as a result of long-term semantic development. In this article, using several examples from Old Czech, I show how the enantiosemic status of words results from the development of lexical units or (sub-)systems. In the first example, the verb ublížit (to harm) has gained (on the background of words blízký, bližní, přiblížit, etc.) negative conceptual content through the systemic usage of the directional meaning of the prefix u-. In another example, the verb odpravit has changed its meaning from ‘to arrange regularly’ to ‘to murder’ during its own complicated semantic development (‘to make sth rightly’ → ‘to punish sb rightly’ → ‘to put sb to death’ → ‘to murder’). Finally, it is shown that the meanings ‘to love’ and ‘to hate’ of the Old Czech verb náviděti have become the result of a double progressive artificially-created opposition to the initial common Slavic nenáviděti – the previous concept, presented both in linguistic and in popular literature on its polysemy, is thus incorrect.