According to Brayley's undated Topographical History of Surrey "...In the garden of a little ale-house grew a pear tree, the fruit of which was so hard and worthless that it acquired the name of 'Iron Pear Tree'. Bonwick, the landlord who was much troubled with gout, brewed his own beer, and to avoid the trouble of fetching water from a distance he sank a well near the pear tree. After drinking the beer brewed with this water, he found himself cured of his complaint..."
For a detailed discussion concerning these bottles see Jonathan Horne, A Catalogue of English Brown Stoneware from the 17th and 18th Centuries, nos. 36 and 37. Another example was sold in these Rooms, 10 February 1986, lot 40