Where does “písečný” come from?

písečný (Czech) comes from Czech Písek, from Polish piesek, from Proto-Slavic pěsъkъ, from Proto-Indo-European pē(n)s-u-ko-.

písečný (Czech): sand

Definitions

Step	Language	Word	Meaning
1	Czech	Písek	—
2	Polish	piesek	Diminutive of pies; young or small dog
3	Proto-Slavic	pěsъkъ	sand
4	Proto-Indo-European	pē(n)s-u-ko-	—

písečný — Etymology, Origin & Word History | Etymology Explorer