The Oxford Introduction to Indo-European states that Germanic *hailaz (>Engl. <whole>) derives from the same root as Greek (Hesychius' gloss) <koi^lu> "good". Earlier etymologies usually postulate *kailos. My question is, why does the Greek word have the circumflex accent? Does it suggest that the Greek form goes back to an earlier *kowilu or *kosilu? (If so, then the Greek word is not cognate, and the other etymology is probably better. I take it that the diphthong *ai is postulated because of Welsh <coel> "omen", in which *ai regularly becomes <oe>, correct?. I've forgotten, what does *oi become in Welsh? <u>?)
Andrew