I'm thinking it may be a way to ameliorate what you say, so as not to cause undue offense, as in the rising intonation at the end of a sentence, apparently originating in Oz but having gained widespread use(age) among American teen-age girls in the last decade....(?*) ['awaiting wet-noodle flogging' emoticon]Oh, Gawd, are we back to Kylie Mole again? Reeeelly? Well, I mean, she g.. she go.. - she just goes!
The use of 'eh' as an ending emphasis on sentences actually originates in that den of all iniquities, Auckland, New Zealand. It travelled (well) across the Tasman to Oz, where it was taken up with gusto by the non-native native population and probably the native native population as well. From there it could have gone anywhere.
The use of "but" at the end of a sentence is definitely anastrophic, and does mean "however" or "as well", depending on the context. It underwent a little craze here a few years ago, died out, then got revived courtesy of a beer ad on TV. I notice, however, that it is dying out again. I don't know if it originated in NZ. Personally, I suspect those non-native native Ozzies again ...
