Where does “ὅστις” come from?

ὅστις (Ancient Greek) comes from Ancient Greek ὅς, from Proto-Indo-European yós, from Proto-Finnic wiša, from Proto-Indo-Iranian wišás, from Proto-Indo-European wisós — fluidity, slime, poison; poison; poison; slime;...

ὅστις (Ancient Greek): indefinite relative pronoun: whoever, whichever;...

Definitions

indefinite relative pronoun: whoever, whichever;...

Ancestry of “ὅστις”, step by step

ὅστις traces back through two separate lines of ancestry.

via Ancient Greek ὅς

Step	Language	Word	Meaning
1	Ancient Greek	ὅς	this; who, which, that; his, her, its
2	Proto-Indo-European	yós	that, who, which
3	Proto-Finnic	wiša	—
4	Proto-Indo-Iranian	wišás	poison, venom
5	Proto-Indo-European	wisós	fluidity, slime, poison; poison; poison; slime;...

via Ancient Greek τίς

Step	Language	Word	Meaning
1	Ancient Greek	τίς	"interrogative"; who?; what?
2	Proto-Indo-European	*kʷís	—

Words derived from “ὅστις”

Every word from Proto-Indo-European wisós →Every word from Proto-Indo-Iranian wišás →Every word from Proto-Finnic wiša →