I think it is "coffadwriaeth" not "Coffadwrineth":
https://wiki.familysearch.org/en/Welsh_GravestonesEr coffadwriaeth am In remembrance of
Er coffadwriaeth parchus am In respectful remembrance of
Er coffadwriaeth serchog am In loving remembrance of
Er coffadwriaeth serchus am In loving remembrance of