Etymology
The origin of the name is the subject of scholar discussions. Hungarian linguists and historians suggested the derivation from the Hungarian ''sojó, só folyó'' (salt water, river) already in the 19th century. Newer theories associate the name with ''sió'' referring to fast streams. According to Slovak linguists the name is pre-Hungarian (''Slaná'': salt river) and most likely not associated with the salinity but with the salt road existing already in times of Great Moravia. The supporters argue by numerous Slavic toponyms in the river basin and by local names related to ''soľ'' (salt) and Moravia like ''Moravce'', ''Soľár'', ''Solišče'', ''Soľka'', ''Soľník'', ''Morava'' (according to this interpretation the Hungarian name is a later translation).References
Rivers of Hungary Rivers of Slovakia International rivers of Europe {{Slovakia-river-stub