Sometimes when Aussies are trying to trick a foreigner they say, "Fair dinkum, mate!" So some Aussies bs while using that expression. Aussie humour is to make you believe falsehoods and they delight in fooling foreigners like Yanks. I knew an old geezer who was visiting Memphis. Some Yank asked him where he was from and he said South Carolina. The Yank said, "Gee, I wouldn't have picked that?" The Aussis thought that fooling Yanks was funny. I thought that was just being stupid. He had a Dundee hat and would have crowds around him because he said he was Crocodile Dundee when people asked if that was who he was. Now, this bloke wasn't being fair dinkum.
One Asian guy asked his mates at work for a good Aussie name for himself. His name is now "Murphy"! You have to watch out for the Aussies.