ENThe article analyzes semantic changes in Latvian helonymy helonymy: names of bogs, marshes, and swamps. Onymization and transtoponymization are identified as the semantic techniques of word-formation used most commonly in Latvian helonyms. Thus, the investigation showed that 80 out of 85 well-known primary helonyms are formed in the process of onymisation i.e. the conversion of common nouns into proper names, and 40 of them have the meaning of bogs and swamps. Most of the primary helonyms belong to the layer of the Baltic inherited lexicon, and their semantics are mainly related to the physiogeographic characteristics of the site. There are relatively few metaphorical helonyms in the material analyzed, and sometimes it is not possible to determine whether the helonym has a metaphorical transfer of meaning or whether the creation of the name has been motivated by an externally perceptible feature. The material analyzed also contains a relatively small number (21) of metaphorical helonyms related to the mythological worldview. Their distribution is quite pronounced in the region around the Daugava, and extralinguistic causes are likely to be the explanation. In the material analyzed quite often the second component of compound and wordgroup helonyms does not correspond to the semantics of helonyms. The original form of the name can be retained even if the object itself has changed or has even disappeared. In the article, these cases are associated with transtoponymization, or a change of place name category. Helonyms are a specific category of toponyms, and their analysis should be done by also taking into consideration the names of meadows, forests and lakes. Keywords: helonym, semantic word-formation, onymization, transtoponymization, metaphor. [From the publication]