Veles's name has attracted sustained comparative attention because it appears to be etymologically related to a cluster of words for death, the dead, or the underworld found across neighbouring Baltic languages, most directly the Lithuanian veles, spirits of the dead, and Velnias, the Lithuanian devil-figure who, like Veles, is associated with cattle, magic, and opposition to the thunder-god Perkunas, the close linguistic and functional cousin of Perun. This resemblance, a Slavic cattle-and-underworld god and a Baltic cattle-and-underworld devil figure sharing both a name-root and a rival relationship with their respective thunder-gods, is one of the more frequently cited pieces of evidence for a shared Balto-Slavic religious inheritance predating the historical split between the two language families, since Baltic and Slavic are recognized by linguists as unusually closely related branches of the Indo-European family.
Some scholars extend the comparison further into wider Indo-European territory, though these more distant comparisons rest on less secure ground than the closer Baltic-Slavic connection. Because the pairing of Veles and Perun in the Rus-Byzantine treaties is one of the most solid pieces of evidence for pre-Christian Slavic religion, the parallel Baltic pairing of Velnias and Perkunas, attested independently through Lithuania's own richer folklore record, which preserved paganism considerably longer than the Christianized Slavic lands, gives scholars a useful second data point for testing how much of the reconstructed opposition between thunder-god and underworld-god reflects a genuine shared inheritance rather than a modern pattern imposed after the fact.