Where does “подберёзовик” come from?

подберёзовик (Russian) comes from Russian берёза, from Old East Slavic береза, from Proto-Slavic bèrza, from Proto-Balto-Slavic berźas, from Proto-Indo-European bʰerHǵos — birch.

подберёзовик (Russian): birch bolete (Leccinum scabrum)