Chleb is not even a Polish word or a slavonic at all. It comes from the Anglo-Saxon word loaf.
it does not come from the Anglo-Saxon loaf -
Slavic chleb and English loaf come from the same Germanic word - it was accepted in Slavic (proto Slavic) through the contact with Gothic settlers that made their way from Baltic Coast (Gdańsk area) down south to the Black Sea - it was pretty probable Slavs (proto Slavs back then) didn't make bread as we know it now (with the use of 'zakwas' or yeast) and just learned to make it through the contact with the Gothic people.
and apart from it- difference between pronounciation of 'caritas' and 'charytatywny' is strange, because the second word is derivated from the first one :~
must be the influence of Greek missionary activity - see Cyryl and Metody in Polish wiki and then open the English counterpart of the article