Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
dyghow
←
Breton
dehou
(cognate)
←
Proto-Celtic
*dexsos
(inherited)
←
Welsh
de
(cognate)
←
Irish
deas
(cognate)
←
Scottish Gaelic
deas
(cognate)
←
Manx
jiass
(cognate)
→
Cornish
dyghowbarth
(compound)
→
Cornish
a-dhyghow
(compound)