bottled in the barn, n. — Green’s Dictionary of Slang

bottled in the barn n.

[pun on SE bottled in bond, bottled and then held in a Customs’ warehouse until the appropriate duty is paid]

(US) illicitly distilled whisky.

1917		Hunter-Trapper 34 84/1: Our guide for the night, on starting out, partook freely from a long black bottle (bottled in the barn).
1923		Annals Amer. Academy Politial and Social Science 109 133/2: People have discovered that ‘bottled in the barn’ carries an exceptionally high percentage of headache and other more serious maladies.
1935		J. Conway World to Win 116: It’s aged in the woods and bottled in the barn. It’s all right. [...] If it doesn’t peel the varnish off the furniture, it’s harmless for man or beast.
1941		‘More Tennessee Expressions’ in AS XVI:1 Feb. 446/2: bottled in the barn. Liquor. ‘Bottled in the barn is hard on the nerves.’.
1956		N. Algren Walk on the Wild Side 126: Luke ducked around the rear of a negro shanty and returned with a pint of Bottled-in-the-Barn.
1970		R. Heinlein in Galaxy 30 138/1: Coffee? Or we can find some Old Kentucky Rat Poison, bottled in the barn.