Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Proto-Celtic
*onkus-tus
→
Irish
agus
(inherited)
→
Scottish Gaelic
agus
(inherited)
→
Manx
as
(inherited)
→
Middle Irish
ocus
(inherited)
→
Old Irish
ocus
(inherited)