Where does “stil” come from?

stil (Middle High German) comes from Old High German stil, from Latin stilus, from Proto-Indo-European (s)teyg- — to be sharp; to sting.

Ancestry of “stil”, step by step

Step	Language	Word	Meaning
1	Old High German	stil	—
2	Latin	stilus	A pointed instrument; stake, pale, spike; A...
3	Proto-Indo-European	(s)teyg-	to be sharp; to sting

stil — Etymology, Origin & Word History | Etymology Explorer