Approximately 400 years ago, there was a small pond and on its bank was a huge banyan tree. A shepherd boy from Vailankanni used to carry milk everyday to a rich man in Nagapattinam which is ten kilometers away. On an unusually hot summer day, the boy, after quenching his thirst with the water from the pond, rested for a while in the shade of the banyan tree which stood beside the pond. Soon the boy fell into a deep slumber. Suddenly he was startled by the vision of a Lady of celestial beauty holding a lovely child in her arms. The boy could not take his eyes off the Lady of unmatched beauty, so spell bound was he by this heavenly vision. The Lady greeted him with a motherly smile and condescended to ask him for some milk for her child. He joyfully gave her some milk for her child and seeing a bewitching smile spread over the face of the heavenly baby, the boy experienced deep satisfaction.
The story of the apparition of the Lady and Child and the miraculous brimming over of the milk, spread like wild fire throughout the neighbourhood. The Christians in Nagapattinam were convinced that the vision was that of the Blessed Virgin Mary with the Child Jesus. Their hearts overflowed with joy at the thought of Our Blessed Mother deigning to choose such an unobtrusive place as Vailankanni to make her apparition. From that day onwards the tank has come to be known as 'Matha Kulam' (Our Lady's Tank). Innumerable miracles are taking place even today by applying it on diseased persons. A chapel now stands at the place where Mary appeared to the shepherd boy.
When he reached the home of the rich man he begged to be excused for his unusual delay and for the shortage of milk. But, when the lid of the milk pot was lifted, lo and behold!, the pot was brimming over with milk. The boy narrated to the rich man about the apparition he had of a Lady of uncommon beauty with a cherubic child and how he had given a portion of the milk he was carrying, to the child at the Lady's request. He said that he had the unique pleasure of seeing that supernatural Lady feed the baby with the milk he had given. The master was fascinated by the extraordinary phenomenon witnessed by the boy and he hastened to the spot where the Lady had appeared with her child. With great reverence, the gentleman prostrated himself on the holy ground where the Lady had appeared to the boy.