Where does “duos” come from?

duos (Latin) comes from Proto-Italic duō, from Proto-Indo-European dwóh₁ — two.

Ancestry of “duos”, step by step

Step	Language	Word	Meaning
1	Proto-Italic	duō	two
2	Proto-Indo-European	dwóh₁	two

duos — Etymology, Origin & Word History | Etymology Explorer