Examples: cartography card archaeology archetype monarchy legal loyal purse personal cinema kinase car carpenter hippopotamus Mesopotamia dative data date
...
Proto-Celtic *onkus

→ Welsh agos (inherited)
→ Irish agus (mention)
→ Scottish Gaelic agus (mention)
→ Manx as (mention)
→ Middle Irish oc (inherited)
→ Middle Irish ocus (inherited)
→ Old Irish oc (inherited)
→ Old Irish ocus (inherited)