Shugendō (修験道 ) is an ancient Japanese religion in which enlightenment or oneness with kami is obtained through the study of the relationship between Man and Nature. Shugendō literally means "the path of training and testing." It centers on an ascetic, mountain-dwelling lifestyle and incorporates teachings from Koshintō, Buddhism and other eastern philosophies including folk animism. Shugendo practitioners are the most direct lineage descendants of the ancient hijiri of the eight and ninth centuries The focus or goal of shugendō is the development of spiritual experience and power.Here is a link to a longer explanation of Fudo-Myo-o and Shugendō, including some concepts like zanshin and fudoshin.
Friday night we were practicing ten-chi-nage and towards the end of class, Shihan mentioned Fudo-Myo-o as the inspiration for the technique. Since ten-chi-nage can be translated as "heaven and earth throw", Shihan explained a bit about Fudo-Myo-o and how he is portrayed in statues.