Green’s Dictionary of Slang

1. denatured or adulterated alcohol, as drunk by alcoholics, tramps etc.

1926		Amer. Mercury Apr. xxx: Dehorn means bootleg booze [W&F].
1929		V.W. Saul ‘Vocab. of Bums’ in AS IV:5 339: Dee horn—Denatured alcohol.
1931		A. Hardin ‘Volstead English’ in AS VII:2 86: Terms used for intoxicating liquor: Dee-horn.
1934		T. Minehan Boy and Girl Tramps of America (1976) 150: A filthy old drunk, full of dehorn moon.
1942		E.B. Davis ‘Paul Bunyan Talk’ in AS XVII:4 221/1: Dehorn Any kind of drinking liquor.
1958		J.C. Holmes Horn 159: He lived on dehorn alcohol, mulligan.
1964		(con. 1920s–40s) in J.L. Kornbluh Rebel Voices.

2. a person who becomes ill through drinking such liquor.

1925		K. Mullen ‘Westernisms’ in AS I:3 153: In the Northwest he is quite as likely to be a ‘de-horn’.
1931		A. Hardin ‘Volstead English’ in AS VII:2 86: Terms applying to one who drinks intoxicating liquors: De-horn.
1951		M. Shulman Many Loves of Dobie Gillis 215: The Jollity Theater is a crummy burlesque house on Minneapolis’s skid row. It is patronized largely by vagrants, winos, dehorns, grifters.