A derivative of "fair enough", "fair-a-nofski" is a response to a statement or outcome that is assumed to be an absolute truth despite being based on no fact whatsoever. "Fair-a-nofski" denotes scepticism or dis-belief.
The first reported use of the phrase was after Christopher Columbus presented his plans to find a Western route to the Orient to King John II of Portugal (see example).
King John II: ...But Christopher, you cannot sail to the West. You fall off the edge of the Eartn - the Earth is flat!
Christopher Columbus: Fair-a-nofski.