Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
keun
→
Welsh
cŵn
(cognate)
→
Scottish Gaelic
coin
(cognate)
→
Cornish
dowrgeun
(compound)