They are generally long slender rod-shaped tools, with a knob on one end for holding and a rake-like device, sometimes in the form of a human hand, on the other end to perform the actual scratching. Though a backscratcher could feasibly be fashioned from most materials, most modern backscratchers are made of plastic, though examples can be found made of wood, whalebone, tortoiseshell, horn, cane, bamboo or occasionally ivory. Backscratchers vary in length between 12 and 24 ins. (30–60 cm.).
The first backscratchers were used by the Inuit and were carved from whale teeth. However, in recent history it was unquestionably also employed as a kind of rake to keep in order the huge "heads" of powdered hair worn by ladies in the 18th and 19th centuries.
In the past, backscratchers were often highly decorated, and hung from the waist as accessories, with the more elaborate examples being silver-mounted, or in rare instances with an ivory carved hand with rings on its fingers. The scratching hand was sometimes replaced by a rake or a bird's claw. Generally, the hand could represent either a left or right hand, but the Chinese variety usually bore a right hand.
Although not specifically used for only back scratching, young Chiricahua men in training and women going through a puberty ritual traditionally had to use a ceremonial wooden scratcher made from a fruit bearing tree instead of scratching with their fingernails or hands. Young men who did not use the scratcher for scratching were reported to develop skin that was too soft.
Source taken from wikipedia.