Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Proto-Celtic
*koxsā
→
Proto-Brythonic
Ἀργεντοκόξος
(mention)
→
Welsh
coes
(inherited)
→
Irish
cos
(inherited)
→
Scottish Gaelic
cas
(inherited)
→
Old Irish
cos
(inherited)