Where does “сестра” come from?
сестра (Ukrainian) comes from Proto-Slavic sestra, from Proto-Slavic sesra, from Proto-Balto-Slavic swésō, from Proto-Indo-European swésōr, from Proto-Indo-European su-h₁ésh₂-ōr, from Proto-Indo-European h₁ésh₂r̥ — blood.
сестра (Ukrainian): sister; nurse
Ancestry of “сестра”, step by step