Same root family, different evolution. A language changes over thousandss of years and two words which started out almost the same may end up unrecognisably far apart. Consider for example diagnosis and agnostic, or pedicure and impede, each pair of which come from the same starting root but end up having almost unrelated meanings.
CAT-holics 
Woah!
How come matrimony is so distant from patrimony?
Same root family, different evolution. A language changes over thousandss of years and two words which started out almost the same may end up unrecognisably far apart. Consider for example diagnosis and agnostic, or pedicure and impede, each pair of which come from the same starting root but end up having almost unrelated meanings.
regards
J