Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Sardinian
oto
←
Proto-Indo-European
*oḱtṓw
(inherited)
←
Proto-Italic
*oktō
(inherited)
←
Latin
octō
(inherited)