Green’s Dictionary of Slang

1. (orig. US) a blow to the head.

1845		Era (London) 26 Jan. 10/3: Weston planted a nut-cracker with the left.
1859		Matsell Vocabulum 127: nut-cracker. A severe blow on the head.
1889–90		Barrère & Leland Dict. of Sl., Jargon and Cant.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1895		C. Crowe Aus. Sl. Dict. 53: Nut Cracker, a severe blow on the head.

2. the head.

1890–1904

Farmer & Henley Sl. and Its Analogues.

3. in pl., the fists.

1937–84

Partridge DSUE (1984) 812/1: later C.19–early 20.

4. (US) a nightstick.

1922

Edwardsville Intelligencer (IL) 14 Sept. 4/4: The Flappers’ Dict. [...] Nut-cracker: Policeman’s nightstick.

5. (US Und.) a police raid.

1917

F. Packard Adventures of Jimmie Dale (1918) II i: ‘Wot’s de lay?’ [...] ‘Aw, nuthin’! De nutcracker on Chang, dat’s all.’.

6. (US) a psychiatrist.

1958		A. King Mine Enemy Grows Older (1959) 200: But Mirko didn’t seem to care too much for the ‘nutcrackers’ around the place.
1966		J. Susann Valley of the Dolls 360: He was a medical doctor, not a nutcracker.
1994		N.Y. Observer 1 Aug. 5: My nutcracker is a 50ish blond with an accent...She’s a little Jungian [HDAS].