Very simply put, 'up your bum' is the ultimate Australian toast. It's not meant literally ('stick it up your ass and rotate', more the opposite, much like the toast: "mud in your eye". Also, it is very important to say it
the right way. If you go in 'half assed' with this toast, you'll get strange looks (as an American
friend of mine found out, when I recommended him to try it Queensland). Say it with a little confidence and a smile, but don't be aggressive - that's not
the right way to go about things in the broad brown land of oz. Most of all - enjoy this toast with a large, cold sparkling amber beverage under the Aussie sky with a good mate.