Laudator Temporis Acti

The Oxford English Dictionary (OED) says that bumf, also spelled bumph, is short for bum-fodder, and defines it as "toilet-paper; hence, paper (esp. with contemptuous implication), documents collectively." OED s.v. bum defines bum-fodder as "worthless literature" and refers to Latin anitergium.

Anitergium, presumably from anus (arse) and tergeo (wipe), apparently does not occur in classical Latin. Du Cange, Glossarium ad scriptores mediae et infimae Latinitatis, says it is a made-up word:

vox ficta, ut facitergium, cujus notio satis patet. Petrus Damiani lib. I. Epist. 9. Materias congerebat, quibus ad requisita naturae necessaria Fratribus anitergia ministraret.

Holbrook Jackson, Anatomy of Bibliomania, Part XIX (The Misfortune of Books), III (Neglect and Misusage), discusses the use of books as toilet-paper:

But abuse more direct and deliberate has been as common in most times, from their use as packing or tinder to the indignity of sanitary necessity, for although Gargantua discommends paper, and books as such are not named in his famous torcheculatif,² their use in this wise is historically established and has become a byword in French coprology. Avisez-y, doctes: parce que souvent d'espice, ou des mouchoirs du cul.³ There are those also, as that old English aphorist,⁴ who go so far as to class the writer of abundance of Books with the begetter of abundance of Children, as a Benefactor of the Publick, because he furnishes it with Bumfodder and Soldiers. I must perforce be indefinite in such a record, so shall only add one instance in which Carew Hazlitt tells us that not so long since a copy of Caxton's Recuyell of the Hystoryes of Troye was found hanging up in a water-closet at Harrogate, sold to a dealer in Manchester for thirty pounds.⁵ Many times rashly and unadvisedly are good books destined to an indignity which might be deemed infamous and ridiculous for even a newspaper, and if I were disposed to enlarge this theme, here might easily be recalled many unsavoury tales from our own early literature, and I would go on with it, but as Grangousier advised Gargantua, it is a dull theme, so to wander on would be no joke, the curious in such business may look for more in Thomas Dekker, his Gul's Horn-Booke, Dryden's Mac Flecknoe, Swift, etc.

² Rabelais. I, xiii. ³Beroalde de Verville, Le Moyen de Parvenir. xvi. ⁴Laconics, or New Maxims. (1701) 118. ⁵ Book-Collecting. (1904) 124.

Because I am "curious in such business" and "disposed to enlarge this theme," which is far from "dull" to me, I've tried to track down the passages mentioned by Jackson. I had no luck with Swift, but here are Dekker and Dryden.

Thomas Dekker, Gull's Horn-Book, chapter 5:

You shall sharpen the wits of all the eating gallants about you, and do them great pleasure to ask what pamphlets or poems a man might think fittest to wipe his tail with.

John Dryden, Mac Flecknoe, lines 100-101:

From dusty shops neglected authors come,
Martyrs of Pies, and Reliques of the Bum.

In addition, here is a passage from John Oldham, A Satyr. The Person of Spencer is brought in, Dissuading the Author from the Study of Poetry, and shewing how little it is esteem'd and encourag'd in this present Age:

Then who'll not laugh to see th' immortal Name
To vile Mundungus made a Martyr flame?
And all thy deathless Monuments of Wit,
Wipe Porters Tails, or mount in Paper-Kite?

For more on this subject, see here.