IW

The Tibetan term Terton (gter ston) means literally one who discovers or reveals treasure. The treasures that are discovered are called gter ma and are the teachings of Buddhas which have been skillfully hidden by great masters of the past, such as Padmasambhava, to be revealed in a later age.

Dudjom Rinpoche quotes from the The Sublime Sūtra of Contemplation which Subsumes All Merits (Āryasarvapuṇyasamuccayasamādhisūtra):

'O Vimalatejas! The doctrinal treasures of Bodhisattvas, great spiritual warriors who desire the doctrine, have been inserted in mountains, ravines and woods. Dhāraṇis and limitless approaches to the doctrine, which are set down in books, will also come into their hands... For one whose aspiration is perfect the doctrine will emerge from the midst of the sky, and from walls and trees, even though no Buddha be present.'

source: Dudjom Rinpoche's 'The Nyingma School of Tibetan Buddhism: Its Fundamentals and History.' Translated and edited by Gyurme Dorje and Mathew Kapstein. Boston: Wisdom Publications, 1991.