Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Proto-Indo-European
*h₂erg-
→
Breton
arc'hant
(derived)
→
Cornish
arhans
(derived)
→
Cornish
arghans
(derived)