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, Polish Piorun, Czech Perun, Serbian Перун, Bulgarian Перун), 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".
Fittingly, there is a sanctuary to Perun located on a height called Perynь near Novgorod (It is located on the northern shore of Lake Ilmen where Volkhov River starts. Nowadays there is a church and a monastery). In south-western Bulgaria is the Pirin mountain range.
As seen from the cognates above, the name of the thunder god is only to be ascertained in Baltic and Slavic, but mythological connections of the thunderer with oaks, or wooded mountains may be reconstructed to be associated with the Proto-Indo-European word.
Further etymologization was attempted with reference to a verbal root *per- "to strike", in reference to the thunderbolt and the violent nature of a thunder god.
This is well attested (it survives for example in press). A velar extension *per-g- is known from Armenian harkanem "felling trees, slaying", Old Irish orcaid "slay" (e.g. in Orgetorix) and Hittite harganu- "destroy". Parjanya is consistent with such a voiced velar, and rather than being cognate to *perk(w)unos appears to be an independent derivation from this root.
A closer relationship of the verbal root to the theonym is not apparent, because of the missing *-kwu- extension, unknown as an Indo-European suffix, and 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.
- Simek (2007:332).
- ^ 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 borrow 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.
- ^ termed "Herrschersuffix" by Wolfgang Meid, Beiträge zur Namenforschung 8 (1957).