Green’s Dictionary of Slang

(US prison) bread and water diet given to a prisoner in the punishment cell.

1912

A. Berkman Prison Memoirs of an Anarchist (1926) 219: Four weeks of ‘Pennsylvania diet’ have reduced me to a skeleton.

(US tramp) apple butter.

1887		Omaha Dly Bee (NE) 17 Sept. 6/1: It proved to be a jar of apple butter (known to the tramp as ‘Pennsylvania salve’(.
1899		J. Flynt Tramping with Tramps 396: pennsylvania salve: apple-butter.
1907		Wash. Herald (DC) 31 Mar. 19/3: Apple butter [...] This utensil was in great demand [...] for comoounding the winter’s allowance of ‘Pennsylvania Salve’.
1914		Pickens Sentinel (SC) 8 Oct. 2/1: The apple crop of North carolina is said to be the largest [...] we should have plenty of ‘Pennsylvania Salve’.
1927		‘Jargon of the Und.’ in DN V 458: Pennsylvania salve, Apple butter.
1930		‘Dean Stiff’ Milk and Honey Route 211: Pennsylvania salve – Apple butter.
1989		H. Rawson Dict. of Invective (1991) 289: Cape Cod turkey, a tongue-in-cheek euphemism for dried salt codfish, and one of a large subset of place names that have been used to flavor different foods, e.g. [...] Pennsylvania salve, apple butter.