Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Old Irish
etar-
←
Proto-Celtic
*enter
(inherited)
←
Old Irish
eter
(mention)
→
Old Irish
etarscara
(affix)
→
Old Irish
etercerta
(affix)
→
Old Irish
doetarrat
(affix)