Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Manx
Glaschu
←
Proto-Brythonic
*glas cu
(derived)
←
Proto-Brythonic
*glas
(mention)
←
Proto-Brythonic
*cöü
(mention)
←
Welsh
cau
(cognate)
←
Irish
cuas
(cognate)