According to a legend, the this tree was planted by the last survivors of the great pest pandemic - the famous black death - that hit the nearby village Linn in 1348/49. After the villagers buried their deads, they planted the tree. According to the legend, the tree will protect the village from the pest as long as it stands.
@Vivaci There is also a legend that the Iris monk Gallus when he walked through Switzerland in the 6th century planted a linden tree at that very spot. As linden trees were a symbol of Christianity, it might be true.
Gallus later founded the monstary which grew into the city of St. Gallen.
@Vivaci Well, it is almost impossible that the tree, which Gallus planted - if he actually planted one - is the one still standing. Its age is estimated at 800 years and not 1'400 years. But it is a beautiful legend.