Green’s Dictionary of Slang

(N.Z. prison) a male visitor or an inmate’s male partner.

1999		D. Looser ‘Boob Jargon’ in NZEJ 13 32: half wit harry n. Male visitor/partner of an inmate.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 83/1: half-wit harry n. a male visitor or male partner of an inmate.