Where does “syskæn” come from?

syskæn (Old Danish) comes from Old Norse systkini, from Old Norse systkin, from Old Norse systir, from Proto-Norse ᛊᚹᛖᛊᛏᚨᚱ, from Proto-Germanic swestēr, from Proto-Indo-European swésōr, from Proto-Indo-European su-h₁ésh₂-ōr, from Proto-Indo-European h₁ésh₂r̥ — blood.

Ancestry of “syskæn”, step by step

StepLanguageWordMeaning
1Old Norsesystkinisiblings
2Old Norsesystkinbrothers and sisters; siblings
3Old Norsesystirsister
4Proto-Norseᛊᚹᛖᛊᛏᚨᚱsister
5Proto-Germanicswestērsister
6Proto-Indo-Europeanswésōrsister
7Proto-Indo-Europeansu-h₁ésh₂-ōr—
8Proto-Indo-Europeanh₁ésh₂r̥blood
Every word from Proto-Indo-European h₁ésh₂r̥ →Every word from Proto-Indo-European su-h₁ésh₂-ōr →Every word from Proto-Indo-European swésōr →