Where does “hēlagon” come from?

hēlagon (Old Dutch) comes from Proto-Germanic hailagaz, from Proto-Germanic hailaz, from Proto-Indo-European *kéh₂ilos.

Ancestry of “hēlagon”, step by step

Step	Language	Word	Meaning
1	Proto-Germanic	hailagaz	holy, sacred
2	Proto-Germanic	hailaz	whole, unbroken, intact; entire, complete; hale,...
3	Proto-Indo-European	*kéh₂ilos	—

hēlagon — Etymology, Origin & Word History | Etymology Explorer