Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Irish
Lughaidh
←
Gaulish
Lucudeca
(cognate)
←
Proto-Celtic
*Lugus
(compound)
←
Proto-Celtic
*dekos
(compound)
←
Old Irish
Lugaid
(inherited)