who developed theories about the power of the part of the mind called the unconscious
Unconscious mind The concept was popularized by the Austrian neurologist and psychoanalyst Sigmund Freud. In psychoanalytic theory, unconscious processes are understood to be directly represented in dreams, as well as in slips of the tongue and jokes.
Psychology The word psychology derives from Greek roots meaning study of the psyche, or soul (ψυχή psukhē, "breath, spirit, soul" and -λογία -logia, "study of" or "research").[8] The Latin word psychologia was first used by the Croatian humanist and Latinist Marko Marulić in his book, Psichiologia de ratione animae humanae in the late 15th century or early 16th century.[9] The earliest known reference to the word psychology in English was by Steven Blankaart in 1694 in The Physical Dictionary which refers to "Anatomy, which treats the Body, and Psychology, which treats of the Soul."[10]