John Ford invariably used Navajo Indians as the “extras” in a lot of his Western films. They were the closest tribe on “reservations” to where Ford liked to film especially to his favourite location Monument Valley.
To get some sort of “revenge” for being portrayed in the films as members of other tribes,either Apache,Comanche or Cheyenne,and whenever they were told to add “authenticity” by speaking in their own “tongue” then they would use obscene or comic dialogue unbeknown to the film makers. When played to a Navajo “audience” the films would cause uncontrollable laughter and mirth!
Navajo “code talkers” were used by the US Marines in the Pacific during WWII because their complex unwritten language was unbreakable by the Japanese!