Green’s Dictionary of Slang

(US) to make or distribute illicitly distilled whisky .

1972		J.S. Hall Sayings Old Smoky 88: Bootleggin’, bootlaggin’ [...] Making bootleg (moonshine) liquor. Sometimes shortened to ‘leggin’, etc. [Ibid.] 92: Lag. Short for bootleg. ‘I didn’t ’lag myself. My business was farmin’ [DARE].
1991		Ruff Call to Assembly 56: Bootlegging was the center of Muscle Shoals’s social commerce [...] The enormous appeal ‘leggin’’ enjoyed in our world, I always suspected, was rooted in the fact that it was so deliciously outside the law [DARE].