Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Irish
fogas
←
Irish
agus
(doublet)
←
Middle Irish
focus
(inherited)
←
Old Irish
ocus
(derived)
→
Irish
aice
(link)