Where does “potrhat” come from?

potrhat (Czech) comes from Czech po-, from Old Czech [[po-]], [[pó-]].

Ancestry of “potrhat”, step by step

Step	Language	Word	Meaning
1	Czech	po-	Perfective aspect, as in "požádat" ask; After, as...
2	Old Czech	[[po-]], [[pó-]]	—

potrhat — Etymology, Origin & Word History | Etymology Explorer