As Guest ozchick above says, it's an expression I have never heard used in Oz, certainly in the parts of Oz in which I have lived! I remember hearing "kicked the bucket", and more recently "fallen off the perch/twig/branch". My late father-in-law used to say "so-and-so has fallen off the twig" - he was over 80 by then and was probably wondering how long he had left. He died 2 days before his 89th birthday, 10 years ago. I think it was his way of facing up to the inevitable without getting too emotionally involved.

Cheers
JennieG