How did the letter Z come to be associated with sleeping/snoring?

In fact it has made itself into its own meaning – it no longer needs explanation and is generally accepted world wide as a representation of sleeping. The reason it even became what it now is, is almost lost, such as the meaning of the wrong end of the stick. I’ll let you figure that one out.

https://english.stackexchange.com/questions/27045/how-did-the-letter-z-come-to-be-associated-with-sleeping-snoring