Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Breton
kas
←
Proto-Brythonic
*kas
(inherited)
←
Proto-Celtic
*kassis
(inherited)
←
Proto-Indo-European
*keh₂d-
(root)
←
Middle Breton
cas
(inherited)