Green’s Dictionary of Slang

1. trousers.

1791		Argus 11 Apr. 3/3: The fair debaters never once uttered the name of this odious part of a man’s dress [i.e. leather breeches]; upon whichMrs Montague declared they were truly and properly to be called unmentionables, as the prudes of the age had titled them.
1824		Literary Magnet 183: Hast thou [...] left in disgust thy troubled and troublesome couch, hurried on thy don’t-name-’ems, morning gown, and slippers.
1828		Atheneum 15 Feb. 386/1: Lastly, his nether garments, compassing in their colossal volume so glorious a rotundity of thigh: Heavens, such a pair of unmentionables!
1830		Stamford Mercury 14 May 4/3: A gentleman, arrayed in a most splendid pair of untalkaboutables.
1830		N. Ames Mariner’s Sketches 106: [of Chinese women’s dress] Underneath this frock was that garment [i.e. a form of trousers] that has as good a claim to be called ‘inexpressible’ or ‘unmentionable’ as the corresponding one, belonging, of right, to our sex.
1833		Albany Microscope (NY) 1 June n.p.: Joshua [...] pulled down the legs of his unmentionables, which [...] had slipped up very considerably for want of straps.
1833		M. Scott Tom Cringle’s Log (1862) 129: In my downfall the catastrophe of my unmentionables had been grievously rent.
1836		Cheltenham Looker-On 20 Feb. 4/1: A gentleman in a red coat and blue unutterables.
1836		Library of Fiction 57: I found [...] my extra wardrobe to consist of one pair of azure unwhisperables.
1837		Knickerbocker (N.Y.) ix (Mar.) 288: How could he see about procuring himself a pair of unwhisperables?
1838		‘Alfred Crowquill’ Seymour’s Humourous Sketches (1866) 9: A short white apron concealing his unmentionables.
1838		Monthly Mag. Apr. 354: The very time he ever put on the first pair of leather unutterables, made for him by Mr. Stickemin.
1842		Whip & Satirist of NY & Brooklyn (NY) 9 Apr. n.p.: That fashionable muscian who got the seat of his unwhisperables torn off .
1843		T. Haliburton Sam Slick in England I 132: The moment I stopt, ghost kinder jumped forward, and seized me by my mustn’t-mention’ems, and most pulled the seat out.
1843		N.Y. Sporting Whip 28 Jan. n.p.: If we, the bewhiskered and breeched members of the community were in fancy that by sticking a bologna sausage into the laps of our unwhisperables we improved out appearance [etc.].
1843		R. Carlton New Purchase I 202: Its seat was [...] wonderfully smooth and glistening from the attrition of linsey garments, tow inexpressibles, and oily buckskin unmentionables.
1844		Bradford Observer 15 Feb. 5/4: His un-talk-aboutables were tuned down, and [...] a volley of hard snowballs were fired away at his bare posterior.
1846		Bell’s Life in Sydney 18 Apr. 2/5: [She] was charged [...] with stealing a pair of unmentionables and two shoes from a gentleman mariner who she had under her protection the previous evening.
1848		W.E. Burton Waggeries and Vagaries 74: Mr. Brattle dressed himself in a new bright blue coat [...] and a pair of large and showy unwhisperables.
1849		Sam Sly 10 Mar. 3/3: He forgets that he used to ride on a donkey cart, with a pair of red plush ‘unmentionables’ on.
1850		Fast Man 13:1 n.p.: Home. Dressed for the evening—immense cross bar unwhisperables—patent boots.
1851		Manchester Spy (NH) 24 May n.p.: He [i.e. a dog] [...] seized the seat of his ‘unmentionables‘.
1855		A.W. Cole Legends in Verse 234: The page’s thin legs are shaking under / Their pretty don’t-name-’ems (whose spacious dimensions / Might accommodate legs of much greater pretensions.
1857		Bell’s Life in Victoria (Melbourne) 12 Dec. 3/4: [F]ull dress— at least immaculate so far as white waistcoats, black unmentionables, and French polished extremities constitute the same.
1859		Sunbury American (PA) 25 June 1/5: While retreating through the woods and through the tangled fern, / He tore his mustn’t-mention-’ems, and had to put on hern.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 242: UNUTTERABLES.
1860		Kentish Gaz. 7 Feb. 5/4: That very poker [...] would have scarcely singed a Scotsman’s unwhisperables.
1865		Kentish Gaz. 22 Aug. 2/4: They have thrust their pretty feet and ankles through our unmentionables, unwhisperables, unthinkaboutables; and they are skipping along the streets.
1866		Wild Boys of London I 123/2: The heavy toff sat down just behind the kerb where there was a nice thick pool of mud into which he deposited the nether part of his best unmentionables.
1870		Hamilton Spectator (Vic.) 21 Sept. 3/2: The gentleman, in a ‘Tommy Dodd’ chintz jacket, snow shirt bosom, satin unmentionables, and shoes with large rosettes.
1874		J. Greenwood Wilds of London (1881) 8: ‘Molly,’ who studied to an atom of sugar the flavour of her Thomas’s grog, and was so sedulous as to the spotlessness of his unmentionables.
1877		‘The Fashionable Coaley’ in Laughing Songster 99: I did my green ‘don’t name ’ems’ doff, / For moleskins which look’d well.
1877		Edinburgh Eve. News 7 June 2/1: Donning his buckled shoes and the ‘unutterables’ which are a cut between the kilt and the garments of ordinary trousered humanity.
1879		Nat. Police Gaz. (NY) 4 Oct. 4/3: It was only with difficulty that she could keep her brother’s ‘unmentionables’ from falling off.
1879		C.J. Kickham Knocknagow 101: The doctor glanced at Bob Lloyd’s unmentionables, and rushed up the stairs like a man bent upon throwing himself out of a window.
1880		Nat. Police Gaz. (NY) 30 Oct. 9: [pic caption] An Old Bachelor Gets Caught in the Matrimonial Net and [...] Finds the Unmentionables of Four Predecessors, which are Kept as Relics.
1881		Bulletin (Sydney) 16 Apr. 3/1: The colt objected, and wound up by seizing the unhappy actor by the seat of his unmentionables.
1883		J. Greenwood Tag, Rag & Co. 94: We saw Daniel Lambert’s coat and his unmentionables.
1884		Western Mail (Wales) 7 Apr. 3/8: Dr Price appeared clad in the well-known green unwhisperables.
1890		Sunderland Daily Echo 11 Feb. 3/2: Unmentionables — Great sale this day of Men’s Tweed Trousers.
1890		Dead Bird (Sydney) 13 Dec. 3/1: When it comes to a schoolmaster taking down his umentionables for however innocent a purpose [etc].
1893		Worcs. Chron. 23 Sept. 4/5: The three-pronged drag [...] was quickly fetched and skilfully fixed, in the seat of the victim’s must-n’t-mention-’ems.
1894		Mirror of Life 26 May 11/3: [H]e saw a person in corduroy unmentionables, an old grey jacket, and minus a hat.
1895		Crowe Aus. Sl. Dict. 91: Unutterables or Unwhisperables, trousers.
1903		Globe (London) 24 Oct. 1 3: Bifurcated unwhisperables offer no resistance to the wind [...] [F&H].
1904		Truth (Brisbane) 10 Apr. 5/3: [S]o back to town she came [...] in high dudgeon, and proferred a straight-out demand for those unmentionables.
1906		Marvel 27 Oct. 390: Fragments of his unmentionables were waving in the breeze from the top of the gate.
1910		Sun. Times (Perth) 22 May 2nd sect. 12/4: A bald-headed bloke dressed black plush coat, unmentionables of the same material, and black silk stockings.
1920		Ade Hand-made Fables 132: When Pa’s red Unmentionables with the Glass Buttons became too Intimate and Itchy, they were chopped down for Ulysses or Grover.
1922		Joyce Ulysses 332: His little man-o’-war top and unmentionables were full of sand.
1928		Exeter & Plymouth Gaz. 7 Mar. 6/6: There was a time when to use the word trousers was almost an indication of a dirty mind. [...] They had been called [...] inexpressibles, indescribables, unwhisperables, mustn’t-mention-ems, sit-upons, sine qua nons, and unutterables.

2. (also don’t-mention-its) the genitals.

1824		Pierce Egan’s Life in London 31 Oct. 315/1: White-feather slipped, and to support himself caught hold of his antagonist's unmentionables.
1839		Crim.-Con. Gaz. 18 May 153/1: I saw Enock Radman, the Omnibus Conductor, showing his unmentionables to the little girls in Dulwich [...] You ought to be flogged at the cart’s tail.
c.1900		A. Cairene Sixfold Sensuality 67: All the way home they were kissing, hugging, squeezing, and playing with each others unmentionables [Ibid.] 91: Undressing each other quite naked, playing with each others ‘don’t-mention-its’.

3. (Aus.) the legs.

1881		Bulletin (Sydney) 19 Mar. 8/4: Gazing on the marvellous, statuesque, symmetry of our ballet queens’ unmentionables.
1904		Sydney Sportsman (Surry Hills, NSW) 25 May 6/2: The ‘player’ who deliberately seized Albert Conlon by the — oh, no, we never mention it— and swung him round till he nearly dismembered the poor fellow, should be barred.

4. underwear.

1832		Satirist (London) 29 July 246/3: The list of hats, shawls, caps, bonnets, garters, and many unmentionables, which were lost, we have before us.
1833		Ely’s Hawk & Buzzard (NY) Sept. 14 n.p.: P.S. A few pair of red flannel unmentionables are wanted. [signed] red flannel drawers.
1884		‘Experiences of a Cunt Philosopher’ in Randiana 19: I suppose if I hadn’t met you it would have been the ‘Royalty’ front row, Florina, they say, has taken to forgetting her unmentionables lately.
1904		Sydney Sportsman (Surry Hills, NSW) 5 Oct. 2/3: [T]he one who wears petticoats turns somersaults and stands on her hands, quite long enough for bald-headed Johnniedom to count the frills on her unmentionables.
1929		S. Ornitz Haunch Paunch and Jowl 105: Generally the gents found a miniature chemise or a tiny pair of unmentionables.
1934		R.E. Howard ‘Mountain Man’ in Action Stories Mar.–Apr. 🌐 This man McGoorty rode into Perdition a few hours ago in his unmentionables.
1953		‘John Eagle’ Hoodlums (2021) 147: She was over the bed pushing her unmentionables into the tan suitcase.
1960		(con. c.1918) D. Holman-Hunt My Grandmothers and I (1987) 14: Unmentionables are socks and drawers.
2005		J. Stahl I, Fatty 218: Pretty soon she was ripping her unmentionables off.