The word Naga originates from India and is a Sanskrit word where "Nag" means snake or cobra. Therefore Nagas (TIbetan: kLu) are a class of snake-like beings that dwell in a variety of locations ranging from oceans, rivers, lakes and other waterways or underground subterranean regions. Many Nagas can have extremely high realisation and are considered protectors of the Dharma. There are also Nagas who are not enlightened and can therefore cause obstacles for humans. Sickness and disease associated with the skin are often believed to be caused by discontented Nagas. This is one of the many reasons that bodies of water, such as lakes, are greatly respected and great care is taken to avoid pollution. Also, special Naga days are observed in the Tibetan calendar to help create harmony between both realms.