The old name of Sankhu is Sarkarapur. The Sarkara means Sakhkar (Sugar). Probably because it was a place where sugar is available, so it is called Sarkara. Gum Vihara is made up of the word Gum. Gum means forest. As there are monasteries in the forest, it may be called Gum Vihara. The Gum word is not Sanskrit, so it may be a pre-Lichhavi language. There is a Stupa on the east side of the place where the Vajrayogini temple is now, in this sense it can be said that this temple was formerly a monastery.
Books like Lhadre Kathang and Sanglingma mention Sankhu Vihara. It’s said that the monastery should be in a secluded place away from the human settlements, where the dogs barking can be heard softly but can be reached, is exactly assimilate with this monastery. The monolithic caves here are said to have been the abode of ascetics. This should be a buddhist center, especially for the devotees who practice in such monolithic caves.
It is said that Siddha Yogis including Nagarjuna performed sadhana in these caves. That is why these caves are called Asi Siddhayogi (Eighty Siddhas) Cave. But over time, Hinduization seems to have taken place. Prajna Paramita (Wisdom Perfection text) is taught here while the priests are Vajracharya. Vajrayogini is called in Tibetan as Dorje Naljyorma. The initiation of Dorje Naljhyorma is considered as a rare and excellent initiation.
Vajrayogini is considered to be one of the eight mothers of Guru Rinpoche. It is located in the forest a little above Sankhu at a distance of about 12 km from Boudhanath or Jhyarang Khasyor in Kathmandu. It is said that the Licchavi king Manadeva built the Ugratara Vajrayogini monastery in the sixth century. Above this monastery is the monastery of Chandeshvari (Ekajati) or Mantrarakshika.