Thanks. Makes sense, I just got confused when I read the Australian's use it as short for Mongrel.http://www.collinsdictionary.com/dictionary/english/mong
http://www.oxforddictionaries.com/definition/english/mongoloid
It's a shortening of mongol which is a further shortening of mongoloid which was a term often slung at people with Down's Syndrome.
Not a lot of people know that...sadly.