Reading some (more) Jeremy Clarkson recently I was struck by the number of "modern" expressions which are to be found and discussed in his writing which are to be found in New Zealand verbiage.
Two examples are the term "whatever" and the use of "reflexive pronouns - the awful "and a drink for yourself, sir?" I hasten to add that Clarkson criticises the latter, heavily, while bemoaning the fact that he is a bit old to use the former credibly.
Why have these expressions found their way into the New Zealand vernacular? Oddly, various other English linguistic habits have not - or at least to no great degree. We have not, for example, taken up Cockney rhyming slang with any great conviction - and where we have we generally don't know why. Even more strangely there is no consistency to what moves and what doesn't.
Australia has for instance not only taken on the rhyming slang notion (the Bengal lancer – cancer, accessible only via the Australian accent) but has developed its own form. My favourite example was their terming (N.Z.) cricketer Mark Greatbatch, "Scones" - apparently from the notion of "a great batch of scones".
So language travels inconsistently as to form and content. Quite why I am unsure... a bad case of whatever – or to use another imbecilic abuse which is popular “random”.