Where does “septum” come from?

septum (French) comes from Latin saeptum, from Latin saeptus, from Latin saepio, from Proto-Indo-European seh₂ip- — to cram, fence.

Ancestry of “septum”, step by step

Step	Language	Word	Meaning
1	Latin	saeptum	an enclosed place; enclosure, fold; a fence,...
2	Latin	saeptus	surrounded, enclosed, having been fenced in;...
3	Latin	saepio	I surround, enclose, fence in; I envelop, wrap; I...
4	Proto-Indo-European	seh₂ip-	to cram, fence

septum — Etymology, Origin & Word History | Etymology Explorer