Reconstruction:Proto-Brythonic/kaw
Proto-Brythonic
Etymology
Certainly cognate with Old Irish cuae, cue (“hollow”) (whence Irish cuas). The ancestral form has traditionally been reconstructed as *kowyos, but Zair observes that this is incompatible with the Brythonic descendants (in particular Proto-Brythonic *kow would regularly result in Breton **kaou) and instead proposes Proto-Celtic *kawyos.[1] Cognate with Latin cavus, and therefore a Doublet of *koudọd (< Latin cavitātem).
Descendants
Reconstruction notes
An Old Cornish or Middle Cornish descendant is not directly attested, but a cognate form *kew can be inferred from a number of toponyms.[2] By contrast Cornish kow is a neologism, perhaps formed by analogy with Welsh cau in comparison with pairs such as Welsh cnau, Cornish know (“nuts”) (from Proto-Brythonic *know), and Welsh crau, Cornish krow (“gore”) (from Proto-Brythonic *krow).
References
R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke et al., editors (1950–present), “cau”, in Geiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies