Samding Dorje Phagmo Twilight language or secret language is a rendering of the Sanskrit term sāṃdhyābhāṣā (written also sāndhyābhāṣā, sāṃdhyabhāṣā, sāndhyabhāṣā; Wylie: dgongs-pa'i skad, THL gongpé ké) or of their modern Indic equivalents (especially in Bengali, Odia, Assamese, Maithili, Hindi, Nepali, Braj Bhasha and Khariboli).
As part of an esoteric tradition of initiation, the texts are not to be employed by those without an experienced guide and the use of the twilight language ensures that the uninitiated do not easily gain access to the knowledge contained in these works.
As Bucknell and Stuart-Fox state: The fivefold classification presented in the tantras is remarkably comprehensive, embracing objects of every conceivable type; it includes the infamous set of "five Ms" (fish, meat, wine, mudrā, sexual intercourse) and even a set of five "body fluids" (faeces, urine, blood, semen, flesh).
In addition it includes sets of doctrinal principles, such as the five skandhas (factors of existence), the four kāyas (Buddha-bodies) and the triad prajña, upāya, bodhicitta (wisdom, means, enlightenment-mind).
For example, prajña, upāya, and bodhicitta are identified with the triads female/male/union, Amitābha/Akṣobhya/Vairocana, and so on, and are thus implicitly assigned to the water, fire, and space groups respectively.