Where does “oniche” come from?

oniche (Old French) comes from Latin onyx, from Ancient Greek ὄνυξ, from Proto-Indo-European h₃nogʰ- — claw, nail; nail.

Ancestry of “oniche”, step by step

Step	Language	Word	Meaning
1	Latin	onyx	onyx, yellow marble; A yellowish precious stone;...
2	Ancient Greek	ὄνυξ	claw, nail, hoof, talon; Anything which resembles...
3	Proto-Indo-European	h₃nogʰ-	claw, nail; nail

oniche — Etymology, Origin & Word History | Etymology Explorer