Where does “svigersøster” come from?
svigersøster (Norwegian Bokmål) comes from Norwegian Bokmål sviger-, from German schwieger-, from German Schwieger, from Middle High German swiger, from Old High German swigar, from Proto-West Germanic *swegru, from Proto-Germanic swegrō, from Proto-Indo-European sweḱrúh₂ — father-in-law.
svigersøster (Norwegian Bokmål): a sister-in-law
Ancestry of “svigersøster”, step by step