Where does “пѣсня” come from?

пѣсня (Russian) comes from Proto-Slavic pěsnь, from Proto-Slavic pěti, from Proto-Indo-European poiH-.

Ancestry of “пѣсня”, step by step

StepLanguageWordMeaning
1Proto-Slavicpěsnьsong
2Proto-Slavicpětito sing
3Proto-Indo-EuropeanpoiH-—
Every word from Proto-Indo-European poiH- →Every word from Proto-Slavic pěti →Every word from Proto-Slavic pěsnь →