Answer:
The code talkers of WWII were from the Navajo tribe.
Navajo has no alphabet or symbols, and is spoken only on the Navajo lands of the American Southwest. One estimate indicates that less than 30 non-Navajos, none of them Japanese, could understand the language at the outbreak of World War II.
The idea to use Navajo for secure communications came from Philip Johnston, the son of a missionary to the Navajos.