Green’s Dictionary of Slang

1. (also hard knut, hard log) a tough person, a dangerous enemy, anything difficult to achieve; thus attrib. and hardnutted, tough, ruthless.

1881		N.Z. Observer (Auckland) 22 Jan. 181/4: The lady evangelist has cracked so many hard nuts that he thinks that even Belinda may be softened.
1884		E. Nye Baled Hay 79: I will ‘pass in my checks’ without a whimper or a cry, And die as I have lived – ‘a hard nut’.
1899		E.W. Hornung Amateur Cracksman (1992) 63: He was a hard nut, a much older man than myself.
1901		G. Fitzmaurice ‘The Disappearance of Mrs. Mulreany’ Weekly Freeman 16 Nov. (1970) 11: The Lord preserve us, he is a hard nut.
1905		West Australian (Perth) 25 Aug. 2/6: I knew there were a few hard nuts about, who were watching an opportunity to rob him while drunk.
1912		Ade Knocking the Neighbors 196–7: it was proven that he stuck Pins into his Grandmother and blew up Elderly Gentlemen with Cannon Crackers and set fire to Houses and was a hard Nut in general.
1914		Bulletin (Sydney) 6 Aug. 26/1: Three times within a fortnight in three distinct oyster halls I have seen damage done to hard ‘knuts’ by mere waiters; and I take this opportunity of advising gay devils, night owls, toughs and naughty boys generally to be more Broosmithian in their treatment of waiters and barmen than they have found necessary in the past.
1920		Bulletin (Sydney) 19 Feb. 16/3: Rolfe, the hard-nut Melbourne merchant.
1923		Dundee Courier 18 Dec. 4: Commissioner Cadman [...] was a notorious character and a ‘hard nut’.
1926		Wood & Goddard Dict. Amer. Sl.
1929		A.J. Barr Let Tomorrow Come 63: I trimmed a hard log, and for the same reason.
1934		D.L. Sayers Nine Tailors (1984) 228: Here’s this Cobbleigh – a hard nut, by all accounts.
1959		Galton & Simpson ‘The Picnic’ Hancock’s Half-Hour [Radio script] Stone me, this one’s going to be a hard nut to crack.
1962		F. Norman Guntz 15: Some of them were hard nuts then and still are.
1970		T. Parker Frying-Pan 40: I can’t think of any others, except perhaps a few of the hard nuts.
1978		S. Longstreet Straw Boss (1979) 384: I saw we had to be as hardnutted as industry.
1986		J. Sullivan ‘The Longest Night’ Only Fools and Horses [TV script] I’m a right villain I am! A real hard nut!
1998		I. Welsh Filth 128: She’s a fuckin hard nut awright.
2008		Camden New Journal (London) Rev. 4 Sept. VII: A typical Cockney hardnut who has a planning councillor in his pay.
2012		D. Whish-Wilson ‘In Savage Freedom’ in Crime Factory: Hard Labour [ebook] Warner could obviously see that Danny was no hard nut.

2. an incorrigible person.

1900		Ade More Fables in Sl. (1960) 181: Convinced that they were Children of Belial and pretty hard Nuts in general.
1914		M. Glass Potash and Perlmutter 49: I always thought Abe Potash was a pretty hard nut.
1953		T.A.G. Hungerford Riverslake 113: He’s a hard nut.
1988		A. Payne ‘The Last Video Show’ in Minder [TV script] 53: You’re a right hard nut and I’m well impressed.
1999		Guardian Guide 18–24 Sept. 5: This heat-packin’ Philadelphia hardnut had two objectives.