But where the hell does the v come from?

I have had Australians tell me that they are a lazy people when it comes to speaking. They regularly shorten words and add an o or ie on the end. For example truck drivers are truckies. Breakfast is brekkie. A smoke break is a smoko. These terms aren't slang either, but are used in everyday and formal conversation. The most interesting and madding I have found in arvo though. It means afternoon. It is pronounced ah-vo with the r dropping out almost entirely. I hear it all the time from radio and tv to people at work or in public. The maddening thing is where the hell did that stupid v come from? No one can tell me where it come from. I can kinda see if you heavily slur afternoon into something like avernoon, but you have to be really drunk to to slur your words that bad. Or at least I do.