Siddham is the East Asian afterlife of an Indian script. It descends from the Gupta form of Brahmi through the stage called Siddhamatrka, the script of north Indian Buddhist manuscripts in the middle of the first millennium CE. Its name comes from the auspicious formula siddham, may there be accomplishment, with which scribes opened a text. As Buddhist monks carried Sanskrit sutras and dharani along the Silk Road into China, the script travelled with them, since translators needed the Indian originals beside their Chinese renderings, and mantras in particular were held to lose power in translation and so were kept in Indian letters.
From China the script reached Japan in the early ninth century with Kukai, founder of the Shingon school, and Saicho of Tendai, both of whom had studied in Tang China. In India itself Siddhamatrka was gradually replaced by Devanagari and its relatives, and the script died out in its homeland. In Japan, renamed shittan, it was preserved, taught, and elaborated in an unbroken scribal lineage, so that today the script survives principally in Japanese temples, a thousand miles and a thousand years from its origin, one of the clearest examples anywhere of writing kept alive purely by liturgy.