Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
arth
←
Proto-Brythonic
*arθ
(inherited)
←
Proto-Celtic
*artos
(inherited)
←
Proto-Indo-European
*h₂ŕ̥tḱos
(inherited)
→
Old Irish
art
(cognate)