Complex sentence: Rebirthing-breathwork grew out of the work of Leonard Orr and his followers, who first used the term "rebirthing" to describe the technique, which was the subject of the book "Rebirthing in the New Age", Orr co-wrote with Sondra Ray.
Split into simpler sentences: Rebirthing-breathwork grew out of the work of Leonard Orr. The name rebirthing was first used by Orr and his followers to describe the technique and became the subject of the book "Rebirthing in the New Age", which Orr co-wrote with Sondra Ray.