Pictured above is Three Fingers, a Plains Indian, communicating with an
Indian agent, Major Stouch, in Indian sign language.  Today's sign
language for the deaf is based on gestures first used in Indian tribes. 
The two-fingered gesture shown here refers to war paint.  Native Americans
sometimes used sign language instead of speaking, and sometimes along with
spoken words, especially when telling stories.  Sign language became
popular among whites through games and imitations of Indian gestures, and
also largely through the Boy Scout movement.  It was included in the
Handbook of the British Boy Scouts as a suggestion for a worldwide "scout"
language.