Green’s Dictionary of Slang

jigger n.3

[SE jig, to shake, with idea of jigger n.1 too as under lock and key ]
(US)

1. [late 18C–19C] (also chigger) a clandestine, illicit still.

2. [19C] (UK Und., also jigger man) one who operates an illicit still and sells the liquor; also attrib.

3. [19C] bootleg liquor; also attrib.

4. [mid–late 19C] a drink of spirits, a dram; also attrib. [SE in 20C+].

5. [mid-19C+] a small glass or metal cup, a measure used in mixing cocktails.

6. [1920s] (US) a young man who frequents soda fountains in the hope of picking up girls.

In compounds

jigger stuff (n.) [stuff n. (5a)]

[early–mid-19C] liquor made at a secret still.

jigger worker (n.) [SE worker/worker n.1 (1)]

1. [mid-19C–1900s] a seller of illicitly distilled spirits.

2. [late 19C] a drinker of such illegal spirits, esp. whisky.