Buckram is a stiff cloth, made of cotton, and still occasionally linen, which is used to cover and protect books. Buckram can also be used to stiffen clothes. Modern buckrams have been stiffened by soaking in a substance, usually now pyroxylin, to fill the gaps between the fibres. In the Middle Ages, "bokeram" was fine cotton cloth, not stiff. The etymology of the term is uncertain; the commonly mentioned derivation from Bokhara is, according to the Oxford English Dictionary, uncertain.