Where does “tr̥s-nó-s” come from?

tr̥s-nó-s (Proto-Indo-European) comes from Proto-Indo-European ters- — dry.

Ancestry of “tr̥s-nó-s”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	ters-	dry

tr̥s-nó-s — Etymology, Origin & Word History | Etymology Explorer