Off the hook has been a 'saying' for the past century and a half, meaning 'got away' or 'escaped'. Maybe somebody involved in Big Brother has been saying it recently, but there is no way he can claim it as his!
QM - one particularly loathsome BB individual did use it a lot, but to mean something other than the accepted definition. Can't really remember but I think it was an adjective of approbation for a fellow (female) housemate.