Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
Icelandic
þekja
←
Proto-Germanic
*þakjaną
(inherited)
←
Old Norse
þekja
(inherited)
→
Luxembourgish
decken
(cognate)