Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
onan
←
Breton
unan
(cognate)
←
Proto-Celtic
*oinos
(derived)
←
Manx
unnane
(cognate)
←
Proto-Indo-European
*óynos
(derived)
→
Breton
unan
(cognate)
→
Manx
un
(cognate)