Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Proto-Indo-European
*-ad[[-tus]]
→
Irish
-as
(inherited)
→
Manx
-ys
(inherited)
→
Old Irish
-as
(inherited)