Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Welsh
coeg
←
Proto-Brythonic
*koɨg
(inherited)
←
Proto-Celtic
*kaikos
(inherited)
←
Proto-Indo-European
*káykos
(inherited)
→
Welsh
genau-goeg
(compound)
→
Welsh
coegog
(suffix)
→
Irish
caoch
(cognate)