Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Welsh
ysgaw
←
Breton
skav
(cognate)
←
Proto-Celtic
*skātom
(cognate)
←
Cornish
skaw
(cognate)
←
Middle Welsh
ysgawd
(cognate)
←
Middle Breton
scau
(cognate)
→
Welsh
eirin ysgaw
(compound)
→
Cornish
skaw
(cognate)