Green’s Dictionary of Slang

1. a prison [nick n.³ (2a)].

1953		B. Behan Scarperer (1966) 12: But I th-thought you were the other side – in the shovel – in Parkhurst. [Ibid.] 22: The shovel and pick, the nick. The Joy. Jail.
1958		(con. 1940s) B. Behan Borstal Boy 210: He’s either been in the shovel or on the trot.
1989		J. Morton Lowspeak 128: Shovel – prison.
2000		J.J. Connolly Layer Cake 28: They’re been in and out of the shovel since approved school.
2007		N. ‘Razor’ Smith Raiders 276: Most of the professionals he trusted were [...] stuck in shovel.

2. an Irishman [ mick n.¹ (1a)].

1992

R. Puxley Cockney Rabbit.