Perkūnas
Perkūnas (Lithuanian: Perkūnas, Latvian: Pērkons or Pērkon,Old Prussian: Perkūns, Finnish: Perkele, Yotvingian: Parkuns) was the common Baltic god of thunder, one of the most important deities in the Baltic pantheon. In both Lithuanian and Latvian mythology, he is documented as the god of thunder, rain, mountains, oak trees and the sky.
The name continues PIE *Perkwunos, cognate to *perkwus, a word for "oak", "fir" or "wooded mountain". The Proto-Baltic name *Perkūnas can be reconstructed with certainty. Slavic Perun is a related god, but not an etymologically precise match. The names Fjörgynn as a name for Odin, and Fjörgyn, mother of Thor, have been proposed as cognates. Finnish Perkele, a name of Ukko, is considered a loan from Baltic.
Another connection is that of terpikeraunos, an epithet of Zeus meaning "who enjoys lightning".
The name survives in Modern Baltic as Lithuanian perkūnas ("thunder"), perkūnija ("thunder-storm"), and the Latvian pērkons ("thunder"), "pērkona negaiss" ("thunderstorm" or "Pērkons' storm"). Alternative names in Latvian are Pērkoniņš (diminutive), Pērkonītis (diminutive), Pērkona tēvs (direct translation would be Father of Thunder but it might be interpreted as God of Thunder instead), Vecais tēvs (Old father).
...
Wikipedia