The difference between 'faith' in a more religious sense and the 'faith' of your example is that for the latter, the evidence that you have is reasonable in lig

The difference between 'faith' in a more religious sense and the 'faith' of your example is that for the latter, the evidence that you have is reasonable in light of the claim. Knowing your great grandmother's nickname doesn't significantly affect your life, and assuming your mother isn't a compulsive liar, there's little reason to doubt her. Furthermore, it also strikes me as the kind of information that would probably be passed down intact because it's easy to remember.