Where does “avopiirakka” come from?

avopiirakka (Finnish) comes from Finnish piirakka, from Russian пиро́г, from Old East Slavic пирогъ, from Proto-Slavic pirogъ, from Proto-Slavic pirъ — fest; party.

avopiirakka (Finnish): open pie, quiche

Definitions

open pie, quiche

Ancestry of “avopiirakka”, step by step

Step	Language	Word	Meaning
1	Finnish	piirakka	pie; pierogi, pirog; pasty
2	Russian	пиро́г	pie
3	Old East Slavic	пирогъ	—
4	Proto-Slavic	pirogъ	type of pie?
5	Proto-Slavic	pirъ	fest; party

Every word from Proto-Slavic pirъ →Every word from Proto-Slavic pirogъ →Every word from Old East Slavic пирогъ →