Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
French
combe
←
Breton
komm
(cognate)
←
Gaulish
*cumba
(mention)
←
Proto-Celtic
*kumbā
(derived)
←
Welsh
cwm
(cognate)
←
Irish
com
(cognate)
→
Welsh
cwm
(cognate)