Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Manx
-ag
←
Proto-Brythonic
*-ọg
(derived)
←
Proto-Celtic
*-ākos
(derived)
←
Manx
-agh
(doublet)
←
Old Irish
-óc
(inherited)
→
Irish
-óg
(cognate)
→
Manx
-agh
(doublet)