"Psycho" means mind. "Somato" means body. Psychosomatic refers to symptoms of a bodily illness which exist only in the mind. Many mental illnesses cause you to feel symptoms like pain or discomfort. These are not entirely imaginary, though many people think that is what the term means. The ill person is in actual discomfort - the only problem is that there is no place on the body that you can treat to relieve the discomfort.