"Fairdinkum" is not colloquial. It is a proper word used by all classes of society and has many meanings just like alot of other words in the English language, even John Howard used it when asking Saddam Hussein to comply with UN 1441 and the rest of the world had no apparent trouble understanding what he meant, including George Bush. Try doing some research and getting some accurate results from the same before making this sort of judgement. On the subject and dealing with your complex about spelling, neither Australia or the United States invented the English language. The big difference here is that we didn't re-invent it to suit ourselves like the US did.

Lastly I made no prepresentation about whether I knew anything about /xyzzy. When you reply to comments you always belittle others about how much you believe they know. For the record I don't know of it's origins and quite frankly it is not important to me if it came from a game or from where-ever. I made a script once that included an alias that altered that reply to "[censored] happens" which some people found more amusing. Did I ask if they knew the origin of the remark? Of course not. I have better things to do with my time than constantly compare my knowledge to that of others. If you know everything then good luck to you.