Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
why
←
Breton
c’hwi
(cognate)
←
Proto-Celtic
*swīs
(inherited)
←
Welsh
chi
(cognate)
←
Old Irish
síi
(cognate)