Where does “çinco” come from?

çinco (Old Spanish) comes from Vulgar Latin cinque, from Latin quīnque, from Proto-Italic kʷenkʷe, from Proto-Indo-European pénkʷe — five.

Ancestry of “çinco”, step by step

Step	Language	Word	Meaning
1	Vulgar Latin	cinque	five
2	Latin	quīnque	—
3	Proto-Italic	kʷenkʷe	five
4	Proto-Indo-European	pénkʷe	five

çinco — Etymology, Origin & Word History | Etymology Explorer