Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
kynnyav
←
Welsh
cynhaeaf
(cognate)
←
Cornish
kyn
(compound)
←
Cornish
goyf
(compound)
←
Cornish
(compound)
←
Old Cornish
kyniaf
(inherited)
→
Welsh
cynhaeaf
(cognate)