Where does “s(w)esō” come from?

s(w)esō (Proto-Balto-Slavic) comes from Proto-Indo-European swésōr, from Proto-Indo-European su-h₁ésh₂-ōr, from Proto-Indo-European h₁ésh₂r̥ — blood.

Ancestry of “s(w)esō”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	swésōr	sister
2	Proto-Indo-European	su-h₁ésh₂-ōr	—
3	Proto-Indo-European	h₁ésh₂r̥	blood

s(w)esō — Etymology, Origin & Word History | Etymology Explorer