Green’s Dictionary of Slang

pepper n.

1. [early–mid-19C] hard blows, e.g. in a prizefight or fig. from a volley of bullets; thus pepperer n., a fighter or boxer.

2. [mid-19C-1900s] serious trouble.

3. [20C+] zest, vitality; thus peppery adj.

4. [1940s–50s] (US black/teen) an attractive young woman.

5. [2010s] (UK drugs) heroin [the powdered drug is often light bown].

In compounds

pepper alley (n.) [sense 1 above; but note Pepper Alley, a landing place on the Southwark side of the Thames, equated with crime, violence and debauchery]

[early 19C] a state of being beaten up.

pepper-box (n.)

1. [early 19C] a sharp, hard blow.

2. see also SE compounds below.

SE in slang uses

In compounds

pepper belly (n.) (also hot pepper belly, pepper gut) [the stereotyped Mexican love of hot food]

[1960s+] (US) a derog. term for a Mexican or Mexican-American; thus pepper-bellied adj.

pepper-box (n.) [resemblance]

1. [mid-19C] (US) the head.

2. [1900s] a pistol.

3. see also sl. compounds above.

pepper-castor (n.) (also pepper-caster) [? resemblance]

1. [late 18C] the head.

2. [late 19C] (US) a revolver.

pepper-fly (n.) [dial. pepper-fly, a sand-fly, which can give a painful sting]

[1950s] (W.I.) an irascible, quick-tempered person.

pepperhead (n.)

[1950s] (US) a show-off.