Where does “pěrun” come from?

pěrun (Czech) comes from Proto-Slavic perunъ, from Proto-Indo-European perkunos, from Proto-Indo-European perkʷ- — oak.

Ancestry of “pěrun”, step by step

StepLanguageWordMeaning
1Proto-Slavicperunъthunder, lightning
2Proto-Indo-Europeanperkunosthe thunder god
3Proto-Indo-Europeanperkʷ-oak
Every word from Proto-Indo-European perkʷ- →Every word from Proto-Indo-European perkunos →Every word from Proto-Slavic perunъ →