Where does “jircha” come from?

jircha (Old Czech) comes from Latin hircus, from Proto-Indo-European ǵʰers- — stiff; surprised.

Ancestry of “jircha”, step by step

Step	Language	Word	Meaning
1	Latin	hircus	a buck, male goat; the rank smell of the armpits;...
2	Proto-Indo-European	ǵʰers-	stiff; surprised