Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Old Irish
cern
←
Proto-Celtic
*kernā
(inherited)
←
Old Irish
cernach
(link)
←
Old Irish
cernach
(link)
→
Irish
cearnóg
(derived)
→
Scottish Gaelic
ceàrn
(inherited)
→
Manx
kerrin
(inherited)