Green’s Dictionary of Slang

1. (N.Z. Und.) a pit into which recalcitrant prisoners are placed for punishment; a solitary confinement cell.

1905

Truth (Wellington) 19 Aug. 3: Prisoners frequently complain that if the chief gaoler gets a snout on them they go into the dig-out on the slightest provocation.

2. (Irish) a loan.

1998

J. O’Connor Salesman 347: I need money [...] I thought y’might like to give me a dig-out. A bit of a loan.

3. an act of support.

2005

P. Howard Curious Incident of the Dog in the Nightdress 136: I’m not really sure if Fionn not giving me a dig-out with pikey [...] actually counts as him getting me back for the diary thing.