Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Proto-Celtic
*kanta
→
Breton
gant
(inherited)
→
Welsh
gan
(inherited)
→
Cornish
gans
(derived)
→
Old Irish
cét-
(derived)