A hobby horse (or hobby-horse) is a child's toy horse, particularly popular during the days before cars. Children played at riding a wooden hobby horse made of a straight stick with a small horse's head (of wood or stuffed fabric), and perhaps reins, attached to one end. The bottom end of the stick sometimes had a small wheel or wheels attached. This toy was also sometimes known as a cock horse (as in the nursery rhyme Ride a cock horse to Banbury Cross) or stick horse. (source)