Where does “sāl-” come from?

sāl- (Proto-Balto-Slavic) comes from Proto-Indo-European sal- — dirty, grey; dirt, dirty; grayish, impure gray.

Ancestry of “sāl-”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	sal-	dirty, grey; dirt, dirty; grayish, impure gray

sāl- — Etymology, Origin & Word History | Etymology Explorer