Where does “svärmoder” come from?

svärmoder (Swedish) comes from Swedish svår, from Old Swedish svar, from Old Norse svárr, from Proto-Germanic swēraz, from Proto-Indo-European swēr- — heavy.

Ancestry of “svärmoder”, step by step

svärmoder traces back through two separate lines of ancestry.

via Swedish svår

Step	Language	Word	Meaning
1	Swedish	svår	hard; difficult; troublesome and of bad temper;...
2	Old Swedish	svar	—
3	Old Norse	svárr	hard, heavy
4	Proto-Germanic	swēraz	heavy; grave, grievous, serious, important
5	Proto-Indo-European	swēr-	heavy

via Swedish moder

Step	Language	Word	Meaning
1	Swedish	moder	mother; mother; as in Mother Theresa, Mother...
2	Old Norse	móðir	mother
3	Proto-Germanic	mōdēr	mother
4	Proto-Indo-European	méh₂tēr	mother

Every word from Proto-Indo-European swēr- →Every word from Proto-Germanic swēraz →Every word from Old Norse svárr →