It is often not spelt but said so spelling is something only done infrequently. Even then it is not going to be found in a dictionary so the user would spell it as he thinks. Ask an Aussie to spell the original word and see how they spell it.
Have you lived in the UK with a house full of Aussie house mates? Believe they are under no illusions where it comes from and what it means.
Do you make this stuff up as you go along? Your housemates were obviously pulling your leg