...and I hate to throw a monkeywrench in this mix as it were, but I had also heard it pronounced like the storm, Tie-Phoon. Not saying this is correct, but another variant.
I used to really be into whistles, and horns to a lessor extent. There was a quartery rag called Horn & Whistle that was full of information by folks who really knew a lot about the industry and hobby. Try to locate some back issues or subscribe, I have seen them @ Winterail.