Green’s Dictionary of Slang

(Aus./N.Z.) an exemplar; thus blithering, first-rate.

1908		Sun. Times (Perth) 10 May 1/1: The Hot Waistcoat Competition is the latest [and] Danny’s shirt-waist is a blithered and a joy.
1909		N.Z. Truth 27 Feb. 6/4: Hot stuff flew thick and fast through the thirteenth [...] The round was a blitherer [...]The last was another blithering round.
1912		Bulletin (Sydney) 12 Sept. 18/1: Patronising Party: ‘I hope you are nice, well-behaved boys.’ / The Nipper: ‘I’m not too horrible, Mister, but Jim, he’s a real blitherer.’.
1912		Sport (Adelaide) 15 June 6/2: [of a racehorse] They all know he’s a blitherooster when after it .
1919		W.H. Downing Digger Dialects 11: blitherer — Something supremely excellent.
1924		(con. WWI) A.G. Pretty Gloss. of Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: blitherer. Something or someone excellent.