furphy

Commonly accepted derivation (courtesy wikipedia):
"…from water carts made by a company established by John Furphy: J. Furphy & Sons of Shepparton, Victoria. Many Furphy water carts were used to take water to Australian Army personnel during World War I. The carts, with "J. Furphy & Sons" written on their tanks, became popular as gathering places where soldiers could exchange gossip, rumours and fanciful tales."

Very Australian, this one. Often used in reference to a rumour that is simply not true.

eg. "A new airport? It's a complete furphy."