Green’s Dictionary of Slang

1. a metal instrument, trad. brass, that covers the knuckles, thus strengthening them when delivering a blow; also attrib.; thus knuckledust v., to be hit by someone wearing a knuckleduster [SE f. 1900].

1856		Wash. Sentinel (DC) 17 May 1/3: A formidable instrument used by thieves in New York, and termed a ‘knuckleduster’.
1858		Times 15 Feb. n.p.: knuckleduster... a formidable American instrument, made of brass, which slips easily on to the four fingers of the hand, and having a projecting surface, across the knuckles, is calculated, in a pugilistic encounter to inflict serious injury on the person against whom it is directed.
1859		G.A. Sala Twice Round the Clock 126: A bunch of skeleton keys, a knuckle-duster, and a piece of wax candle, all articles sufficiently indicative of the house-breakers stock-in-trade.
1860		T. Haliburton Season Ticket 294: [He] takes out a pair of ‘knuckle-dusters’ and puts them on his sledge-hammer fists.
1869		Manchester Courier 6 Jan. 6/2: It looked very suspicious to find a man with a ‘knuckleduster’ on a balcony at half-one in the morning.
1872		Schele De Vere Americanisms 320: In fighting, a horrible contrivance is sometimes used, called in savage irony knuckledusters, an iron instrument contrived to cover the knuckles so as to protect them from injury when striking a blow, adding force at the same time, and with knobs or points projecting, so as to disfigure and mutilate the person struck.
1872		Standard ‘Middlesex Sessions Report.’ n.p.: In another box he found a life-preserver, the end of it being loaded with knuckle-dusters, and other things of the same description [F&H].
1880		R. Rowe Picked Up in the Streets 8: He took from his pocket a pair of ‘darbies,’ [...] and slipped them on his fist like ‘knuckle-dusters’.
1882		Sydney Sl. Dict. (2 edn) 5: Knuckle-duster - A large, heavy, or gaudy ring. An iron or brass instrument which protects the knuckles when striking a blow, adding a cruel force to it at the same time. American.
1888		J. Runciman Chequers 84: Four of us were wondering how they could rob the fifth, and that fifth resolved [...] to use his knuckle-duster promptly.
1890		Sporting Times 4 Jan. 1: Take this Knuckleduster and Shooting Iron and Go In for Prizefighting.
1895		C. Crowe Aus. Sl. Dict. 43: Knuckle Duster, a fighting ring - pugilistic term.
1898		Herald (Los Angeles) 25 Sept. 17/5: His aggressors were provided with knuckledusters, revolvers and knives.
1903		A.H. Lewis Boss 14: He struck me with a knuckle duster.
1908		A.N. Lyons Arthur’s 249: I [...] wondered if it hurt one much to be knuckle-dusted in the eye.
1918		S. Bourke & Mornington Jrnl (Richmond, Vic.) 11 July 2/8: I into ’im with a knuckle duster on the bunch of fives.
1925		Black Mask Aug. III 16: I’d slipped on a pair of knuckle dusters – brass knuckles if you get what I mean.
1931		B. Lubbock Bully Hayes 18: He was no hazing, heavy-fisted, knuckle-duster bucko.
1940		Yorks. Post 9 Jan. 8/6: It was alleged that the knuckleduster was worn by O’Malley in a fight he had with Joyce.
1949		N.O. Times-Picayune Mag. 3 Apr. 25/2: A glorious free-for-all ensued, a primitive battle of fists, clubs, rocks, knuckle-dusters and steel bars [DA].
1958		A. Sillitoe Sat. Night and Sun. Morning 86: Luck was always changing. It thumped you with knuckledusters on the back of the neck one minute.
1966		B. Reckord Skyvers I ii: You can ’ave this knuckle-duster for a night for a tanner.
2000		Guardian Guide 18–24 Mar. 52: O’Reilly’s auntie has sent him a knuckle-duster.
2011		S. Kelman Pigeon English 63: A knuckleduster with extra long spikes.

2. a large, gaudy, flashy ring.

1870		Hotten Sl. Dict. Knuckle-duster a large, heavy, or over-gaudy ring; a ring which attracts attention from its size.
1890–1904		Farmer & Henley Sl. and Its Analogues.
1924		G.H. Lawson Dict. of Aus. Words And Terms 🌐 KNUCKLE-DUSTER—Big finger ring.
1935		A.J. Pollock Und. Speaks.
1943		J.B. Hislop Pure Gold and Rough Diamonds 102: A small pick and shovel with a nugget attached used to be a great seller, as was also the heavy signet ring with a nugget on top — ‘knuckle-dusters’ they were called.

3. an amateur boxer.

1910

Bisbee Daily Review (AZ) 20 Dec. 4/3: Knuckledusters themselves do not hang about saloons or have a bunch of ham and eggers in red sweaters and rah rah caps, flocking at their heels.