Where does “hælog” come from?

hælog (Old Swedish) comes from Old Norse heilagr, from Proto-Germanic hailagaz, from Proto-Germanic hailaz, from Proto-Indo-European *kéh₂ilos.

Ancestry of “hælog”, step by step

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

hælog — Etymology, Origin & Word History | Etymology Explorer