Troff is the opposite to peak. Just like on a graph you have the peak, you also have the trough, or 'troff'. The peak is the best as it is the top, and the 'troff' is the worst as it is at the bottom. This therefore means that if something is 'troff' it is the worst it can possibly be.
Harry: Jack, I'm listening to some music about putting a pigeon in a box and sending it off to Rome, It's peak!
Jack: No, Harry, that music is troff, very troff indeed. errr.