Where does “suster” come from?
suster (West Frisian) comes from Old Frisian swester, from Proto-Germanic swestēr, from Proto-Indo-European swésōr, from Proto-Indo-European su-h₁ésh₂-ōr, from Proto-Indo-European h₁ésh₂r̥ — blood.
suster (West Frisian): sister
Ancestry of “suster”, step by step