Hesychasm (from the Greek for “stillness, rest, quiet, silence”) is a mystical tradition and movement that originated with the Desert Fathers and was central to their practice of prayer. Hesychasm for the Desert Fathers was primarily the practice of “interior silence and continual prayer.” It did not become a formal movement of specific practices until the fourteenth century Byzantine meditative prayer techniques, when it was more closely identified with the Prayer of the Heart, or “Jesus Prayer.” That prayer’s origin is also traced back to the Desert Fathers—the Prayer of the Heart was found inscribed in the ruins of a cell from that period in the Egyptian desert. The earliest written reference to the practice of the Prayer of the Heart may be in a discourse collected in the Philokalia on Abba Philimon, a Desert Father. Hesychast prayer was a meditative practice that was traditionally done in silence and with eyes closed—”empty of mental pictures” and visual concepts, but with the intense consciousness of God’s presence.
The words hesychast and hesychia were frequently used in 4th and 5th century writings of Desert Fathers such as Macarius of Egypt, Evagrius Ponticus, and of Gregory of Nyssa. The title hesychast was used in early times synonymously with “hermit,” as compared to a cenobite who lived in community. Hesychasm can refer to inner or outer stillness, though in The Sayings of the Desert Fathers it referred to inner tranquility. ~Wikipedia “Desert Fathers”