https://en.wikipedia.org/wiki/Code_talker
A code talker was a person employed by the military during wartime to use a little-known language as a means of secret communication. The term is most often used for United States service members during the World Wars who used their knowledge of Native American languages as a basis to transmit coded messages. In particular, there were approximately 400 to 500 Native Americans in the United States Marine Corps whose primary job was to transmit secret tactical messages. Code talkers transmitted messages over military telephone or radio communications nets using formally or informally developed codes built upon their indigenous languages. The code talkers improved the speed of encryption and decryption of communications in front line operations during World War II and are credited with some decisive victories. Their code was never broken.