Where does “sahha” come from?

sahha (Old High German) comes from Proto-West Germanic saku, from Proto-Germanic sakō, from Proto-Indo-European seh₂g- — to seek out.

Ancestry of “sahha”, step by step

Step	Language	Word	Meaning
1	Proto-West Germanic	saku	accusation, charge; case
2	Proto-Germanic	sakō	quarrel; charge, case, lawsuit; thing, matter
3	Proto-Indo-European	seh₂g-	to seek out

sahha — Etymology, Origin & Word History | Etymology Explorer