Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Middle French
couster
←
Old French
coster
(inherited)
→
French
coûter
(inherited)
→
Middle French
coustable
(suffix)
→
Middle French
coustage
(suffix)