Where does “*skātu” come from?

*skātu (Proto-Celtic) comes from Proto-Indo-European (s)ḱeh₃- — darkness, shadow.

Ancestry of “*skātu”, step by step

Step	Language	Word	Meaning
1	Proto-Indo-European	(s)ḱeh₃-	darkness, shadow

*skātu — Etymology, Origin & Word History | Etymology Explorer