Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
resek
←
Proto-Brythonic
*rrėdɨd
(inherited)
←
Proto-Celtic
*reteti
(inherited)
←
Middle Cornish
resek
(inherited)
→
Welsh
rhedeg
(cognate)