Where does “diallos” come from?

diallos (Cornish) comes from Cornish di-, from Proto-Celtic dī-, from Proto-Indo-European de — Emphatic or contrastive particle, and, but;...

diallos (Cornish): incapable, incompetent, powerless, unable

Definitions

Step	Language	Word	Meaning
1	Cornish	di-	un-, non-, -less, without
2	Proto-Celtic	dī-	from, of; clothes, clothing; from, away
3	Proto-Indo-European	de	Emphatic or contrastive particle, and, but;...