Green’s Dictionary of Slang

1. one who pretends to be selling smuggled goods, but is in fact selling old or shop-worn stock, obtained cheaply.

1788

Grose Classical Dict. of the Vulgar Tongue (2nd edn).

2. (US) a smuggler of contraband liquor, a bootlegger [abbr.; OED cites legger as abbr. of 1920s+ bootlegger, but sense 1 suggests the practice already existed].

1926		Flynn’s 16 Jan. 640: I sashayed for a legger an’ run into a rube hip agent with a bottle and some jake which helped some [DARE].
1931		Appeal-Gimlet (Marysville, CA) 16 May 3/6: [headline] Booze Loving Bug / With Gimlet Beak / Worries ’Leggers.
1935		N. Algren ‘Thundermug’ in Texas Stories (1995) 74: They brung a Mex ’legger in here one afternoon ’way last fall.
1939		R. Chandler Big Sleep 47: Oh, you mean the ex-legger the eldest girl picked up and went and married.
1970		L. Sanders Anderson Tapes 120: When I was driving for a legger down home we had this old smoke working for us—he could turn out a mighty fine mash.