Green’s Dictionary of Slang

(N.Z.) used in various phrs. of comparison, e.g. mad as a..., skinny as a...

1961		B. Crump Hang On a Minute, Mate (1963) 52: Old Andy mad as a gum-digger’s dog.
1964		R. Helmer Stag Party 83: ‘Musta been a pudgy individual.’ ‘Naw, skinnier ’n a gum digger’s dog, eh?’ [Ibid.] 121: Hunter’s crazy as a gum digger’s dog.
2003		McGill Reed Dict. of N.Z. Sl. 94: gumdigger’s dog, as mad as/as skinny as/as stupid as/as useless as Very mad/skinny/stupid/useless. In the case of skinny, a gumdigger’s bitch is an alternative invocation.
2014		L. Parry Eugenia 45: Ooh, I’m as crook as a gum digger's dog.