The Moomba Festival is Australia's oldest community festival. It's a sort of fireworky, carnival, water sports thing. Great fun, by the look of it.
And moomba? Well, the official line is that it means let's all have fun together in one of the local native Australian languages.
But I'm afraid that moom actually seems to mean buttocks or bottom in that language: and ba does quite often mean up...
It looks as if Melbourne Council's researcher didn't quite understand the answer the native speakers gave him when he asked them for their help.
Word Not To Use Today. Moomba. Though, actually, moom is a rather lovely word for bottom and actually I think that part of the word should be used more often.