Green’s Dictionary of Slang

(N.Z.) a psychiatric institution.

1948		D. Ballantyne Cunninghams (1986) 21: They took John back to the wow because one night at tea he grabbed a knife and reckoned he was going to chop the head off the first one to look up from his plate.
1953		I. Hamilton Till Human Voices Wake Us 46: [A breakdown] usually leads to cutlery swallowing or a ticket for the wow.
1982		G. Newbold Big Huey 30: But when he said ‘gidday mate’ to the magistrate [...] they forgot about taking a plea and just remanded him straight out to the wow.
1993		K. Sinclair Halfway Round the Harbour 38: To get there a boy had to cycle up [...] Gladstone Road (as Carrington Road was then called) past the mental hospital, which everyone called the Wow. I believed that this term meant ‘the loony bin’, another local name. In fact it was so called because of the nearby Whau Creek [DNZE].
2003		McGill Reed Dict. of N.Z. Sl. 235: Wow Area of Avondale suburb of Auckland near Whau Creek where the former psychiatric hospital, now Unitec, is known as the Wow.