Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Middle Irish
cóiced
←
Proto-Celtic
*kʷenkʷetos
(inherited)
←
Old Irish
cóiced
(inherited)
→
Irish
cúigiú
(inherited)