Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Breton
sec'h
←
Proto-Brythonic
*sɨx
(inherited)
←
Latin
siccus
(derived)
←
Old Breton
sech
(inherited)