Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
hil
←
Proto-Brythonic
*hil
(inherited)
←
Proto-Celtic
*sīlom
(inherited)
←
Proto-Indo-European
*seh₁-
(root)
→
Welsh
hil
(cognate)