Where does “September” come from?

September comes from Latin september, derived from Latin septem, meaning "seven," ultimately from Proto-Indo-European septḿ̥.

Ancestry of “September”, step by step

Step	Language	Word	Meaning
1	Latin	september	of September
2	Latin	Septem	—
3	Proto-Italic	septem	seven
4	Proto-Indo-European	septḿ̥	seven

September — Etymology, Origin & Word History | Etymology Explorer