Where does “hendec-” come from?

hendec- (English) comes from Ancient Greek ἕνδεκα, from Ancient Greek εἷς, from Proto-Hellenic hens, from Proto-Indo-European sḗm, from Proto-Indo-European sem- — together, one.

Ancestry of “hendec-”, step by step

Step	Language	Word	Meaning
1	Ancient Greek	ἕνδεκα	eleven
2	Ancient Greek	εἷς	one
3	Proto-Hellenic	hens	cardinal number 1 Previous: n/a Next: *dúwō;...
4	Proto-Indo-European	sḗm	one
5	Proto-Indo-European	sem-	together, one

Words derived from “hendec-”

hendecad

Every word from Proto-Indo-European sem- →Every word from Proto-Indo-European sḗm →Every word from Proto-Hellenic hens →