Where does “pětka” come from?

pětka (Czech) comes from Czech pět, from Old Czech [[pieti]], [[pěti]], from Proto-Slavic pěti, from Proto-Indo-European poiH-.

pětka (Czech): five; ten korunas; try

Definitions

Step	Language	Word	Meaning
1	Czech	pět	five; to sing
2	Old Czech	[[pieti]], [[pěti]]	—
3	Proto-Slavic	pěti	to sing
4	Proto-Indo-European	poiH-	—

pětka — Etymology, Origin & Word History | Etymology Explorer