Where does “*kell” come from?

*kell (Proto-Brythonic) comes from Latin cella, from Proto-Indo-European ḱelnā, from Proto-Indo-European ḱel- — to cover; to incline.

Ancestry of “*kell”, step by step

Step	Language	Word	Meaning
1	Latin	cella	a small room, a hut, storeroom; a barn, granary;...
2	Proto-Indo-European	ḱelnā	—
3	Proto-Indo-European	ḱel-	to cover; to incline

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