Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Proto-Indo-European
*-eh₂ḱos
→
Welsh
-og
(mention)
→
Middle Irish
-ach
(mention)
→
Old Irish
-ach
(mention)