Used as an expression pertaining to particularly hard work ie: 'I had to carry that hod of bricks up 20 flights of stairs, it was absolutely back-breaking!'. However, the phrase came a little to close to the truth a couple of years ago for my mate Terry. He had been driving overnight from visiting his folks in the north of England in a car he had recently bought second hand from a dodgy geezer in Margate when he fell asleep at the wheel, careered over a raised roundabout at 50mph and his 'new' car literally broke in half, as did his back! The dodgy geezer had sold him a 'cut & shut' automobile. He now recieves an invalidity pension but has fully recovered you'll be pleased to hear.