Where does “kvassi” come from?

kvassi (Finnish) comes from Russian ква́с, from Old East Slavic квасъ, from Proto-Slavic kvasъ, from Proto-Indo-European kwh₂et- — to ferment, become sour; to boil, foam.

kvassi (Finnish): kvass

Definitions

kvass

Ancestry of “kvassi”, step by step

Step	Language	Word	Meaning
1	Russian	ква́с	kvass
2	Old East Slavic	квасъ	—
3	Proto-Slavic	kvasъ	leaven, fermented drink
4	Proto-Indo-European	kwh₂et-	to ferment, become sour; to boil, foam

Every word from Proto-Indo-European kwh₂et- →Every word from Proto-Slavic kvasъ →Every word from Old East Slavic квасъ →