Green’s Dictionary of Slang

1. the best, the superlative.

1917		‘Whale Song’ in J.J. Niles Singing Soldiers (1927) 10: Oh, Jonah got a gas-bomb and said this is the nuts.
1930		(con. 1910s) L. Nason A Corporal Once 53: ‘Ain’t you the nuts!’ said Stuffy enviously.
1939		P. Di Donato Christ in Concrete 224: Yeah kiddo – big steel is the nuts!
1947		E. Condon We Called It Music 84: ‘This is really a band,’ he said. ‘Definitely the nuts. There’s nothing better.’.
1955		P. Rabe Benny Muscles In (2004) 237: ‘He really thinks you’re the nuts, Benny, really proud of you.’.
1962		H.S. Thompson letter 17 Apr. in Proud Highway (1997) 331: That is the nuts, my man, and nobody yet has shown me anything to beat it.
1967–8		Baker et al. CUSS 164: Nuts, The Extraordinary, unusual.
2000		J.J. Connolly Layer Cake 151: The place is the nuts.
2011		J.J. Connolly Viva La Madness 166: Sonny [has] already sent for an expert in the field [...] this Smiler kiddie is the nuts.

2. something bad or objectionable.

1919		in Our Navy June 21: This packet is all the nuts in amillion fruitcakes and the ship is just as popular with me as a glass eye at a burlesque show.
1929		A.J. Barr Let Tomorrow Come 39: ‘How about those stories in the papers, Red?’ ‘Them’s the nuts,’ is his answer.
1951		Green & Laurie Show Biz from Vaude to Video 569: It’s the nuts – Sime’s brushoff to anything spurious.
1958		R. Prather Scrambled Yeggs 60: ‘This is the nuts,’ I said. ‘I’ve got work to do.’.