Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
kesten
←
Breton
kistin
(cognate)
←
Ancient Greek
κᾰ́στᾰνᾰ
(derived)
←
Latin
castanea
(derived)
→
Breton
kistin
(cognate)