bumf: [20] The earliest, literal, but now long discontinued sense of bumf is ‘toilet paper’ (first recorded in 1889), which does much to elucidate its origin: it is short for bum fodder. The element of contempt is carried over into its modern meaning, ‘unwanted or uninteresting printed material’, which dates from around 1930. [bumf etymology, bumf origin, 英语词源]