Examples: cartography card archaeology archetype monarchy legal loyal purse personal cinema kinase car carpenter hippopotamus Mesopotamia dative data date
...
Middle French -eur
← Old French -eur (inherited)
← Old French -eor (mention)
← Old French -or (mention)

→ French -eur (inherited)
→ French buveur (mention)
→ Middle French ioueur (mention)
→ Dutch -eur (derived)