These splitter linguists have had their say for long enough. The Japanese are clearly just the island branch of Altaic peoples, and the anthropological data is enough. In Mongolia, you're not supposed to whistle inside a ger because it will bring a windstorm. In Korea, whistling at night will bring spirits and snakes too. In Japan, you're not supposed to whistle indoors because either a snake will come - or Tengu will kidnap you. What are Tengu? I'm so glad you asked. Tengu are the indigenous, pre-Buddhist spirits that can create strong winds. By the way, what was the Altaic sky-god's name? Tengri. SPLITTER LINGUISTS, IT'S OVER! IT'S ALL OVER!
Alright. That may be overstating the case, but one has to admit it's otherwise an odd superstition to share.