The country is known by many names. For instance, it was called Lhojong Menjong or the ‘southern land of medicine’ since medicinal herbs grew in abundance. It was also called Ridrag gi yul or the ‘land of the dense forests and mountainous terrain,’ a name based on its landscape. Tsenden key pi jong or the ‘land of cypresses’ is another name as it is a country where cypress (national tree of Bhutan) grew plentifully. After 16th century, people of the country began to call it Druk Yul or the ‘Land of the Thunder Dragon,’ a name derived from Drukpa Kagyu school, (one of the four major schools of Mahayana Buddhism), the main religion practiced in the country. However, to the outside world the country is known as Bhutan.