https://en.wikipedia.org/wiki/Vajrayana
Terminology. In Tibetan Buddhism practiced in the Himalayan regions of India, Nepal, and Bhutan, Buddhist Tantra is most often termed Vajrayāna (Tib. རྡོ་རྗེ་ཐེག་པ་, dorje tekpa, Wyl.rdo rje theg pa) and Secret mantra (Skt. Guhyamantra, Tib.གསང་སྔགས་, sang ngak, Wyl.gsang sngags).The vajra is a mythical weapon associated with Indra which was said ...