Where does “valsche” come from?

valsche (Middle High German) comes from Finnish falski, from Swedish falsk — false; untrustworthy.

Ancestry of “valsche”, step by step

Step	Language	Word	Meaning
1	Finnish	falski	fake, insincere, phony; false, spurious; out of...
2	Swedish	falsk	false; untrustworthy

valsche — Etymology, Origin & Word History | Etymology Explorer