Green’s Dictionary of Slang

porridge n.

1. [20C+] imprisonment [the staple morning diet of such establishments in the UK + pun on stir n.1 (1)/SE stir].

2. [1920s+] (Irish) based on SE porridge, a hotch potch.

(a) a confusion, e.g. a traffic jam.

(b) nonsense; usu. as you have your porridge, you are talking nonsense.

In phrases

SE in slang uses

In compounds

porridge bird (n.) [1980s+] (S.Afr. gay)

1. a flaccid penis.

2. an impotent man.

porridge gun (n.) [the supposed similarity of semen to porridge]

[1990s+] the penis.

porridge hole (n.)

[late 19C] (Scot.) the mouth.

porridge stuffer (n.) (also porridge-stuffer) [stereotypical Scot. food]

[late 19C] (Aus. / N.Z.) a Scotsman.

porridge wog (n.) [wog n.1 (3)]

[1990s+] a derog. term for a Scottish person.

In phrases

stir the porridge (v.)

[1980s+] (orig. Aus.) to have sexual intercourse with a woman immediately after she has had sex with another man, esp. used of the final man in a gang rape.

wouldn’t know (someone) if (they) stood up in my porridge

[2000s] (N.Z.) to profess complete ignorance of someone.