Where does “Τοῦρκος” come from?

Τοῦρκος (Greek) comes from Persian ترک, from Middle Persian twlk', from Old Turkic 𐱅𐰇𐰼𐰜, from Proto-Turkic *tür(ü)k.

Ancestry of “Τοῦρκος”, step by step

Step	Language	Word	Meaning
1	Persian	ترک	crack
2	Middle Persian	twlk'	—
3	Old Turkic	𐱅𐰇𐰼𐰜	—
4	Proto-Turkic	*tür(ü)k	—