Green’s Dictionary of Slang

rotgut n.

[its effects; cf. gut-rot under gut n.]

1. [late 16C+] cheap or inferior beer.

2. [late 17C+] cheap wine.

3. [early 19C+] (US, also rot) cheap whisky.

4. [mid-19C+] cheap alcohol in general.

5. derog. term for soft drinks.

6. [1950s+] illicitly distilled alcohol.