Green’s Dictionary of Slang

thick ’un n.

also thick one
[the dimensions of the coin/foodstuff]

1. a sovereign (£1).

[UK]Hotten Dict. of Modern Sl. etc.
[UK]Worcs. Chron. 12 Nov. 4/1: If you like [...] I will send a few thickuns to bring you and your tamtart [sic] up to Start.
[UK]Illus. Police News 30 Mar. 3/2: If anyone there present wanted a ‘thick ’un’ he coukd let them have it [...] ‘A thick ’un is a sovereign’.
[UK] in G.D. Atkin House Scraps 115: ‘Have you sufficient confidence in me to lend me a sovereign?’ ‘Oh! yes, I’ve the confidence, but I haven’t the thick-un.’.
[UK]Sporting Times 8 Feb. 3/2: [They] presented him with a pin made out of a Jubilee sovereign, and not a mere ordinary common or tea-garden sovereign either, but one a size larger than the usual thick ’un, which turned out to be a shilling carefully gilded.
[Aus]Truth (Sydney) 2 Sept. 7/5: His pals put up their ‘thick ’uns’ with a ‘dead cop’ kind of snigger.
[UK]Marvel XIV:344 June 5: Well, gaffer, you’ve planked down ther thick-’uns straight so far.
[Aus]Sun. Times (Perth) 17 Jan. 4/5: Eighteen thick ’uns for the greatest epic poem in the language!
[Aus]Bulletin (Sydney) 21 July 44/1: I’ve done th’ trick, an’ no narsty questions arst. Ole Ice-cream give me a thick-un fur settin’ on your pal the monkey’s ’ead while ’e pulled your coat an’ weskit off of ’im.
[Aus]Smith’s Wkly (Sydney) 7 June 9/6: Slang of Money [...] A sovereign is a ‘glistener,’ ‘mousetrap,’ ‘new hat,’ ‘quid,’ ‘remedy,’ ‘stranger,’ ‘thick ’un’.
[UK]N. Lucas Autobiog. of a Thief 106: Give me the day when a quid was a golden thick’un, worth twenty shillings.
[NZ]Eve. Post (Wellington) 19 Dec. 19/6: My fares used to pay me in gold — thickuns and ’alf-thickuns without a murmer.
[UK]J. Franklyn Cockney 289: Everyone knows how much a quid is; not everyone could guess the value of a thick-’un.

2. five shillings, a crown (25p).

[Aus]E. Dyson Fact’ry ’Ands 213: He had a naxident — swallered er thick-un.

3. a slice of bread and butter.

[UK]A.J. Vogan Black Police 56: Them Star boys collared me ticket, an [...] I’ll get dollied if fayther cotched me back at ’ome without a thick ’un fur ’im.
[UK]A.N. Lyons Arthur’s in Franklyn Cockney (1953) 99: He will ask respectfully for another cup of coffee and a thick ’un.
[Aus]M. Garahan Stiffs 99: Cawfee, baby’s head small, boiled, no veg, two thick ’uns.
[UK]S. Jackson Indiscreet Guide to Soho 80: Cuppa cawfee and a thick ’un.

4. a silver dollar.

[US]A.J. Pollock Und. Speaks.

In phrases

do someone a thick ’un (v.)

to play a ‘dirty trick’ on someone.

[UK]Sheffield Eve. Teleg. 11 Feb. 4/4: A kind friend, who possessed a stronger love for mischief [...] had, to use his own expresive phrase, ‘done him a thick ’un’.
[UK]Worcs. Chron. 12 May 6/6: You’ve tried to do me a thick ’un, and I’ll do you one.
A. Conan Doyle ‘The Mazarin Stone’ in Case Book of Sherlock Holmes [Internet] ‘Ikey Sanders has split on us.’ ‘He has, has he? I’ll do him down a thick ’un for that if I swing for it.’.
[UK]Eve. Teleg. 27 Nov. 4/2: Pennett burned the summonses, saying, ’I’ll do that bobby a thick ’un’.
half-thick (’un) (n.) (also half-a-thick)

(N.Z.) a half-sovereign, ten shillings.

[UK]Notts. Guardian 24 Aug. 5/4: They were giv’ to me, and I only had ‘half a thick ’un’ for my trouble.
[UK]‘Pot’ & ‘Swears’ Scarlet City 191: Then he began Dutch auctioneering and at last he let me off with half-a-thick ’un.
[UK]C. Rook Hooligan Nights 38: Young Alf pulled from his waistcoat pocket the half thick ’un which was his share of the profits.
[UK]B. Pain De Omnibus 1: The other dye I ’appened ter pick up a extry ’alf-thick-un throo puttin’ money on my opinyun of the Gran’ Neshnal.
[Aus]Bulletin (Sydney) 14 Sept. 13/2: [A]ncient paupers [...] have been surprised by visits and missives from long-lost sons and daughters whose blood warms to the talismanic touch of ‘ ’arf-a-thick-’un.’.
[UK]‘R. Andom’ Neighbours of Mine 216: ‘What on earth is half-a-quid?’ ‘Half-a-thick — I mean sovereign,’ said the youth.