Bootleg

Originally used to denote illicitly-trafficked liquor, and the illicit trafficking itself, in the United States. The smuggler, or bootlegger, would conceal the liquor in his boot-legs. Used in particular during Prohibition (though the Oxford English Dictionary dates the earliest such usage to 1889), but more recently applied to the making and distribution of illicit sound recordings. The OED records the earliest such use in 1951, though the practice probably had its heyday in the second half of the 1960s and the early 1970s, beginning perhaps with Bob Dylan's famous Albert Hall concert in 1966 (which in fact took place in the Free Trade Hall in Manchester). That recording has for many years now been available as volume 4 of what Columbia Records market as "The Bootleg Series".