Bootleg

wiktionary

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boot +‎  leg. Originally a nickname given to smugglers in King George III's reign, derived from the smugglers' custom of hiding packages of valuables in their large sea-boots when dodging the king's coastguardsmen. 

etymonline

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bootleg (n.)

also boot-leg, "upper part of the leg of a boot," 1630s, from boot (n.1) + leg (n.). As an adjective in reference to illegal liquor, 1889, American English slang, from the trick of concealing a flask of liquor down the leg of a high boot. Before that the bootleg was the place to secret knives and pistols. Extended to unauthorized music recordings, etc., by 1957.