Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Breton
-enn
←
Proto-Brythonic
*-enn
(inherited)
←
Welsh
-en
(cognate)
←
Cornish
-en
(cognate)
←
Middle Breton
-enn
(inherited)
→
Welsh
-en
(cognate)
→
Old Irish
-ne
(cognate)