Where does “ędro” come from?

ędro (Proto-Slavic) comes from Proto-Indo-European h₁en-d(ʰ)r-óm, from Proto-Indo-European h₁én — in.

ędro (Proto-Slavic): kernel, core

Definitions

Step	Language	Word	Meaning
1	Proto-Indo-European	h₁en-d(ʰ)r-óm	—
2	Proto-Indo-European	h₁én	in

ędro — Etymology, Origin & Word History | Etymology Explorer