This title is bestowed on the Reverend Hooper in later life:
As the years wore on, shedding their snows above his sable veil, he acquired a name throughout the New England churches, and they called him Father Hooper.
The 'years shedding their snows' refers to how Hooper's hair turns white with age, and this is particularly striking when coupled with the black, or 'sable' veil that he still staunchly refuses to discard.
Hooper acquires the title of Father as he grows older and more venerable. It is symbolic of how, in general, people look up to him for his gravity and wisdom. It shows that, although the mysterious black veil has the effect of driving many individuals in his own parish away from him, on the whole he is still very much respected; the churches still value him as a minister and for the good work he does. Whenever people are in trouble, when they are ill or dying, it is Hooper that they instinctively turn to. In spite of the air of mystery that surrounds him, he provides comfort in times of need, like a true father to his congregation.