Where does “смоляной” come from?

смоляной (Russian) comes from Russian смола́, from Old East Slavic смола, from Proto-Slavic smolà.

Ancestry of “смоляной”, step by step

Step	Language	Word	Meaning
1	Russian	смола́	tar; resin, tar; resin, pitch, tar
2	Old East Slavic	смола	—
3	Proto-Slavic	smolà	—

смоляной — Etymology, Origin & Word History | Etymology Explorer