Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
arghans
←
Proto-Celtic
*arganto-
(inherited)
←
Proto-Indo-European
*h₂erg-
(derived)
←
Old Cornish
argans
(inherited)
→
Cornish
arghansek
(compound)
→
Cornish
arghantti
(compound)