Green’s Dictionary of Slang

(N.Z./UK) a euph. oath.

1941		Baker N.Z. Sl.
1947		C.V. Smith From N to Z 25: [Christchurch] derived its name from a remark passed by the first settler who…was so overcome by the magnificent sight that all he could exclaim was ‘Oh, Christchurch!’ [DNZE].
1963		‘R. Casey’ As Short a Spring 129: Christchurch, look at your bed. You can’t see a doctor like that [DNZE].
1988		McGill Dict. of Kiwi Sl. 28/1: Christchurch!/by Christchurch!/by Christchurch, hooya? euphemistic extension of exclamation ‘by Christ!’, the ‘hooya’ short for ‘who are you?’ a juvenile addition; Partridge suggests a ‘Maorified’ shape of ‘by crikey, who are you?’.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].
2006		P. Shannon Davey Darling 155: Christ-church! Who the hell was this?