It's an old Aussie saying,

Bush week

Presented by Kel Richards

A NewsRadio listener emails to ask for the origins of bush week. Well, bush week refers to fictitious festival when bushies come to town in droves.

Thus the expression bush week is used ironically by someone who suspects they’re being made the victim of a scam or prank

The bushies, of course, are supposed to be a bit slow on the uptake (and perhaps as thick as a brick) so lots greasy larrikins and city slickers try to rip them off. Thus the expression bush week is used ironically by someone who suspects they’re being made the victim of a scam or prank, as in the question “What do you think this is, bush week?” To which the proper response is, “Yes, and you’re the sap!” The first recorded instance of the term bush week is from 1919 – to describe a serious attempt to organise a Bush Festival in the City of Sydney.” Within a few years it was being used ironically, and entered Aussie English as a standard conversational ploy (recorded as such by Sid Baker in 1949).