Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Middle Irish
abacc
←
Proto-Celtic
*abankos
(derived)
←
Proto-Celtic
*abū
(mention)
←
Middle Welsh
afanc
(cognate)
→
Irish
abhac
(inherited)