It seems to be a solution among pastoral cultures for long range communication. It probably arises as one shepherd whistles at another in their local language,

It seems to be a solution among pastoral cultures for long range communication. It probably arises as one shepherd whistles at another in their local language, and the other one whistles back "holy shit, that worked!" I plan on trying it with friends and family next time we go fishing/camping/hiking. A little bit of practice and repetition should be all it takes.