Green’s Dictionary of Slang

horrors, the n.

also blue horrors

1. [mid-18C+] a fit of depression, unpleasant worries.

2. [mid-19C+] delirium tremens; often as in the horrors; ext. as blue horrors; cast-iron/stonewall horrors.

3. [mid-19C+] a hangover.

4. [1920s+] unpleasant reactions suffered during the withdrawal from narcotic drugs.

5. [1930s+] unpleasant experiences (usu. paranoid fantasies) brought about occas. by the effects of drug-taking, usu. smoking cannabis, opium or from taking a hallucinogen.

In phrases

dig the horrors (v.)

see separate entries.