Where does “tetr̥-wó-s” come from?

tetr̥-wó-s (Proto-Indo-European) comes from Proto-Indo-European -wós — Creates adjectives from verb stems.

Ancestry of “tetr̥-wó-s”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	-wós	Creates adjectives from verb stems

tetr̥-wó-s — Etymology, Origin & Word History | Etymology Explorer