Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Icelandic
fimmti
←
Proto-Germanic
*fimftô
(derived)
←
Old Norse
fimmti
(derived)
→
Icelandic
fimmtudagur
(mention)