The author likely calls Coorg a "piece of heaven that must have drifted from the kingdom of God" because Coorg is a beautiful and peaceful place with a natural landscape and a pleasant climate. The author may believe that the beauty and tranquility of Coorg are reminiscent of the kingdom of God and therefore Coorg must have been created by God and drifted down to Earth. This language and imagery is often used to describe places that are seen as particularly beautiful and serene, and it conveys the author's sense of awe and admiration for Coorg.
