-yd

From Middle Welsh -yt, from Proto-Brythonic *-öd, from Proto-Celtic *-o-tūts.^[1]

• (North Wales) IPA^(key): /ɨ̞d/
• (South Wales) IPA^(key): /ɪd/

-yd

1. forming abstract nouns, -ness, -ment

   ‎iach (“healthy”) + ‎-yd → ‎iechyd (“health”)

   ‎claf (“sick, ill”) + ‎-yd → ‎clefyd (“disease”)

   ‎mab (“son”) + ‎-yd → ‎mebyd (“childhood, infancy”)

-yd causes i-affection of internal vowels.

• R. J. Thomas, G. A. Bevan, P. J. Donovan, A. Hawke, et al., editors (1950–present), “-yd”, in Geiriadur Prifysgol Cymru Online (in Welsh), University of Wales Centre for Advanced Welsh & Celtic Studies