Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Welsh
dillad
←
Breton
dilhad
(cognate)
←
Proto-Celtic
*dī-
(inherited)
←
Cornish
dillas
(cognate)
→
Breton
dilhad
(cognate)
→
Cornish
dillas
(cognate)