From IE *perkṷu- "oak-tree":
- Lithuanian Perkūnas, Latvian Pērkons, Old Prussian Perkūns, the god of thunder
- possible cognate Sanskrit Parjanya, the god of rainstorms and thunder
- Thracian Περκων/Περκος, (Perkon/Perkos)
- With suffix -k- dropped via IE *perō(ṷ)nos "thunder, Thunderer", possibly from a connection with *perūn(V) "mountain, rock":
- Slavic Perun (Old Russian Перунъ, Belarusian Пярун, Ukrainian Перун, Polish Piorun, Czech Perun, Serbian Перун, Bulgarian Перун, Slovenian Perun/Perün/Perunk), the god of thunder
- possibly Albanian Perëndi, the god of thunder and storms
- possibly Hittite Pirwa, "the god on a horse", which associated with a rock
- possibly Greek keraunós "thunderbolt"
*perk(w)unos is reconstructed on the basis of Perkūnas. Parjanya is no exact cognate, see below.
The labiovelar is reconstructed due to a Centum word for "oak", "coniferous tree", or "mountain", "coniferous mountain forest", *perkwus. Here also, the labiovelar is non-trivial, and indeed singular in the sequence *-kwu-, its justification being in Latin quercus "oak", the result of an assimilatory Italo-Celtic sound law changing *p...kw to *kw...kw (compare quinque, Irish cóic vs. Sanskrit pañca "five"; coquo vs. Sanskrit pacati "to cook"). Celtic *Ercunia, if cognate, did not partake in the assimilation, advising towards a cautious reconstruction of *perk(w)us.
The original meaning of this u-stem *perkwu- appears to be concept of an oak, a coniferous forest, a mountain forest, or a wooded mountain:
- "oak": Latin quercus, Old High German fereheih "oak", Celtic Hercynia silva. The oak is quite a common motif in myths about Perkūnas. Cognates include Sanskrit parkaṭī "fig tree", the Venetic and Celtiberian ethnonyms Quarquēni and Querquerni, the Ligurian Nymphis Percernibus, Old Norse fjörr "tree", Anglo-Saxon furh (Modern English fir), Old Norse fura, Old High German forha (Modern German Föhre) "pine tree", Old Norse fyri, Old High German forh-ist (Modern German Forst) "pine forest", Old High German Fergunna (the Erzgebirge), Langobardic Fairkuna. Anglo-Saxon firgen "wooded height", Gothic fairguni "mountain".
- A possibly related word *peru-r/n- for "rock" or "mountain" is reconstructed from Hittite peruna, "rock", Sanskrit parvata, "mountain" (Parvati, daughter of Himavant), Thracian per(u), "rock".
The association with oaks can be explained by the frequency with which tall trees are struck by lightning. This is reflected in two beliefs, one being that the Norse god Thor could strike enemies hiding under an oak tree, but not under the smaller beech; the other that oak trees contained a fire within them that lightning could release (or vice versa, that the lightning transferred fire into the tree that explained why wood was effective fuel).
Fittingly, there was a sanctuary to Perun (now a monastery) located on a height called Perynь near Novgorod, on the northern shore of Lake Ilmen, the source of the Volkhov River. There is a Pirin mountain range is in south-western Bulgaria.
As seen from the cognates above, the name of the thunder god is only attested in Baltic, Slavic, and Germanic languages, but mythological connections of the thunderer with oaks or wooded mountains may link to the Proto-Indo-European word.
Further etymological connections were hypothesized with a verbal root *per- "to strike", in reference to the thunderbolt and the violent nature of a thunder god. The name Parjanya itself could also be derived from *per-, though it cannot be strictly cognate with *perk(w)unos, since Old Indic j does not reflect PIE *kʷ. A closer relationship of the verbal root to the theonym is not demonstrable, because the *-kwu- extension is not otherwise attested as an Indo-European suffix, and because of the semantic distance between "slaying" and "tree" or "mountain".
According to Julius Pokorny (IEW), Russian Perunъ "thunder god" and perun "thunderbolt" which likewise lack the velar element are indeed influenced by the root discussed, the activity of "striking down" being associated with the Balto-Slavic theonym by popular etymology.
- European Paganism, p. 221, at Google Books
- Attested in Hellenistic dedications from Galata near Varna (ancient Odessos): IGBulg I2, 283, 283bis.
- In fact, the Albanian word is inseparable from perëndim "West, sunset", perëndoj "to set (about sun)", and isn't connected with this root, see: Орел В. Э. Исконная лексика албанского языка (Балканские этимологии. 6–13) // Славянское и балканское языкознание: Проблемы лексикологии. М.: Наука, 1983. С. 151–152.
- Frisk, Greek Etymological Dictionary
- But most likely Przeginia (and Bereginya) is a loan in Slavic from German *fergunja, see: Николаев С. Л., Страхов А. Б. К названию бога-громовержца в индоевропейских языках // Балто-славянские исследования. 1985. М.: Наука, 1987. С. 152–158.
- Simek (2007:332).
- Mallory, J. P.; Adams, Douglas Q., eds. (1997). "Thunder god". Encyclopedia of Indo-European Culture. Taylor & Francis. p. 582.
- Termed "Herrschersuffix" by Wolfgang Meid, Beiträge zur Namenforschung 8 (1957).