Where does “syster” come from?
syster (Middle Low German) comes from Old Saxon swestar, from Proto-Germanic swestēr, from Proto-Indo-European swésōr, from Proto-Indo-European su-h₁ésh₂-ōr, from Proto-Indo-European h₁ésh₂r̥ — blood.
Ancestry of “syster”, step by step
Words derived from “syster”