I'm wondering whether the usage of the word has changed over time
In my reading of older texts, I have sometimes gotten the impression that "faith" did not mean a belief in God's existence (which was considered self-evident) but a belief in God's mercy. Technically, in the RCC, I think this particular belief is called "hope," (as in faith, hope, and charity)but I think the word faith was often used in its stead.
But I have no examples from texts at the moment to illustrate this.