Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Middle Irish
sechtmad
←
Proto-Celtic
*sextametos
(inherited)
←
Middle Irish
secht
(affix)
←
Middle Irish
-mad
(affix)