Green’s Dictionary of Slang

black as... adj.

used in var. combs. to mean extremely black, usu. of darkness, occas. of race.

[UK]West Kent Guardian 4 July 6/3: Arra, my dear life, at the word she grew as black as twelve o’clock at night.
[UK]Newcastle Courant 13 Feb. 6/2: Disporting themselves on the mountains of coal [...] they returned black as niggers.
[Aus]Sydney Sportsman (Surry Hills, NSW) 9 Jan. 1/2: This last-named black quadruped was [...] as black [...] as the Earl of Hell’s waistcoat.
[Aus]Bulletin (Sydney) 10 Dec. 32/4: The wood-and-water joey, with a blackened pair of eyes – / As black as any nigger’s hide could be.
[US]D. Runyon ‘Baseball Hattie’ in Runyon on Broadway (1954) 643: Her hair that was once as black as a yard up a stove-pipe is grey.
[UK]Gloucester Citizen 3 Oct. 1/3: The ship was as black as the inside of a cow.
[UK]D. Davin For the Rest of Our Lives 311: Tom Bluey stumbled and would have fallen if Tom by a guess in the dark hadn’t caught his arm in time. ‘Black as the inside of a Taranaki cow,’ Bluey muttered.
[NZ]P. Newton Wayleggo (1953) 47: It was too dark—in Casey’s words, ‘black as the inside of a cow’.
[US]W.D. Overholser Buckaroo’s Code (1948) 95: ‘There’s no use looking around down here, boss,’ Gould yelled. ‘Blacker’n the inside of a bull’s belly.’.
[NZ]Our Own Country 132: All through a night as black as a muster’s billy we had seen nothing but the black form of black hills [DNZE].
[Aus]W.E. Harney Content to Lie in the Sun 58: The stubborn will of a good bushman who was powerful enough to force our camel string through a night as black as the ‘inside of a dog’s guts’.
[US](con. early 1950s) J. Peacock Valhalla 169: Goddam but it’s dark. Black as a cat’s ass at midnight.
[Aus]M. Anderson A River Rules My Life 65: It’s as black as the inside of a cow tonight.
[US]F. Elkins diary in Heart of a Man M.R. Elkins (1973) 10 July 41: It was black as Mooney’s goose.
[Aus]J. Wynnum I’m a Jack, All Right 29: If it wasn’t as black as the inside of a cow, I might have some chance of sighting Moutn Hope.
[US]E. Thompson Garden of Sand (1981) 213: If they have a world’s championship [...] and a nigger black as Natoby’s ass takes the cake in them all, I don’t count it as skin off mine.
[Ire]H. Leonard Time Was (1981) Act II: The moon’s gone in. It’s as black as a dago’s armpits.
[US]C. Hiaasen Tourist Season (1987) 357: It’s black as a bear’s asshole and fulla bugs. Why the hell do you wanna go over there on a night like this?
[NZ]McGill Reed Dict. of N.Z. Sl. 23: An intensive in a myriad of phrases, including black as the back end of a bull / a leper’s armpit / midnight in Naseby / Sunday morning in a West Coast coalmine.

In phrases

black as Newgate (adj.) (also black as Newgate wall, dark as Newgate) [Newgate, 19C London’s main convict prison and the site of many executions; its reputation was fig. black]

1. of an expression, frowning, glowering.

[UK]‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 124: ‘As black as Newgate,’ is said of a street lady’s lowering countenance, or of her muslin-dress, when either is changed from the natural serene.
[UK]Cambridge Indep. Press 29 May 9/7: ‘As black as Newgate,’ was a description used by a woman speaking of her husband in Acton Police Court.

2. dirty, e.g. of a garment.

see sense 1.
[UK]Sussex Advertiser 25 Aug. 6/6: It is quite marvellous to behold the improvem,ent [...] in some of those gardens which all along have been as ‘black as Newgate’.
[UK]Liverpool Dly Post 20 Sept. 7/4: I’m sure that Old Bailey is that filthy that they may as well say ‘as black as Newgate’.
[UK]Taunton Courier 26 Apr. 8/4: That thing! (Laughter) Why it was as black as Newgate wall [...] I wouldn’t touch the thing (Laughter).
[UK]Cornishman 22 Sept. 9/5: The water was churned up by compressed air. It was as black as Newgate.
black as Newgate knocker (adj.) (also black as Newgate’s knocker) [see prev.]

1. (also dark as Newgate knocker) of a night, very dark.

[Aus]Bell’s Life in Sydney 1 June 3/1: A gentleman gifted by Providence with a countenance the exact facsimile of the knocker of Newgate.
[UK] in N&Q 6 Ser. iii 248: ‘As black as Newgate knocker’ — I heard this expressive phrase used the other day by a servant.
[UK]G.L. Gower Gloss. of Surrey Words 12: Coming from Croydon on a very dark night the driver remarked, ‘Ay! it is a dark night, dark as Newgate knocker.’.
[UK]P. Shaffer Black Comedy [one-act play] It’s as black as Newgate’s knocker up ’ere. Are you playing one of your saucy games, Mr Miller?
[UK]K. Bonfiglioli Don’t Point That Thing at Me (1991) 143: Outside the night was as black as Newgate’s knocker.

2. very dirty.

[UK]Barltrop & Wolveridge Muvver Tongue 94: Of a grubby-looking person: [...] black as Newgate’s knocker.
[UK]J. Sullivan ‘May the Force be with You’ Only Fools and Horses [TV script] A white male with oriental features who’s as black as Newgate’s knocker!
[UK] in Socialist Rev. (London) 10 May [Internet] When we came in dirty after playing, my mother would say that our hands or faces were ‘as black as Newgate’s knocker’.