Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Cornish
lym
←
Breton
lemm
(cognate)
←
Proto-Celtic
*lim-ā-
(inherited)
←
Proto-Indo-European
*sley-
(derived)
→
Welsh
llym
(cognate)