Where does “Quintilis” come from?

Quintilis (English) comes from Latin Quintilis, from Latin quintus, from Latin quinctus, from Latin quinque, from Proto-Italic kʷenkʷe, from Proto-Indo-European pénkʷe — five.

Ancestry of “Quintilis”, step by step

Step	Language	Word	Meaning
1	Latin	Quintilis	Of Quintilis
2	Latin	quintus	fifth, the ordinal number after "quartus" and...
3	Latin	quinctus	—
4	Latin	quinque	five; 5
5	Proto-Italic	kʷenkʷe	five
6	Proto-Indo-European	pénkʷe	five

Every word from Proto-Indo-European pénkʷe →

Quintilis — Etymology, Origin & Word History | Etymology Explorer