Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Irish
tú
←
Proto-Celtic
*tū
(inherited)
←
Proto-Indo-European
*túh₂
(inherited)
←
Old Irish
tú
(inherited)
→
Irish
agat
(compound)
→
Irish
tusa
(affix)
→
Irish
imreoir
(mention)
→
Scottish Gaelic
thu
(cognate)