Examples:
cartography
card
archaeology
archetype
monarchy
legal
loyal
purse
personal
cinema
kinase
car
carpenter
hippopotamus
Mesopotamia
dative
data
date
...
West Frisian
sechste
←
Proto-Germanic
*sehstô
(inherited)
←
Old Frisian
sexta
(inherited)
→
North Frisian
seekst
(cognate)