Green’s Dictionary of Slang

a woman of doubtful reputation; ext. as a relatively classy prostitute, and a figure defined by Henry Fielding in Tom Jones (1749) as one ‘whom everybody knows to be what nobody calls her’.

1749		Fielding Tom Jones (1959) 518: He had yet no knowledge of that character which is vulgarly called a demirep; that is to say, a woman that intrigues with every man she likes, under the name and appearance of virtue.
c.1758		John F---g Epistle of a Reformed Rake 8: Demi-Reps, Good-natured Girls, Kept Mistresses.
1767		G. Colman Oxonian in Town II i: A demirep of quality.
1772		G. Stevens in Songs Comic and Satyrical 102: [song title] ‘The Demirep or, I Know Who’ .
1776		Caledonian Mercury 23 July 3/3: In the most fashionable circles [...] sharpers, gamblers, knights of the post, divorced harlots and demi-reps.
1784		Bath Chron. 30 Dec. 2/1: A certain demi-rep who figures in the high ranks of Cyrpian votaries, found herself some time ago in a state of delicate perplexity.
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue n.p.: Demy rep, abbreviation of demy reputation, a woman of doubtful character.
1788		G.A. Stevens Adventures of a Speculist I 260: Moll King’s, a coffee-house [...] resorted to by all the Bucks, Bloods, Demireps and Choice Spirits in London.
1797		M. Leeson Memoirs (1995) III 182: A demi rep of some consequence, with her coach and suite of servants.
1802		Sporting Mag. Jan. XIX 218/1: Ladies of fashion are rarely out sooner, fashionable demi-reps not till three o’clock.
1811		Lex. Balatronicum.
1812		Spirit of Irish Wit 230: ‘He would not part with his supper [...] for all the demi-reps and bullies from Cork to Antrim ’.
1821		‘A Real Paddy’ Real Life in Ireland 181: At every place of extravagance she led the van as a first rate demirep.
1831		Navy at Home II 198: A lean fantastical demirep of fashion.
1846		Bell’s Life in Sydney 12 Sept. 3/1: Eliza Brown, a flaming demi-rep, who ‘sets at easy rate her willing charms’.
1848		Thackeray Vanity Fair III 102: So they went on talking about dancers, fights, drinking, demireps, until Macmurdo came down.
1850		E.V. Kenealy Goethe: a New Pantomime in Poetical Works 2 (1878) 336: Demirep, Lacedmutton, Gadder; / Do give over flinging dirt.
1858		‘A. Pendragon’ Queen of the South 111: I cumber it with slang expressions! It’s my fault, I suppose, that such a tongue is spoken by the demi-reps of Australia?
1859, 1860		Hotten Dict. of Modern Sl. etc.
1867		Nat. Police Gaz. (NY) 26 Oct. n.p.: Day after day, week after week, charges are brought against this irrepressible ‘demi-rep’.
1868		Paisley Herald 18 July 3/3: Henri Rochefort [...] was accused of living at the expense of a notorious demi-rep.
1871		C.G. Leland ‘Breitsmann in Italy’ in Hans Breitmann in Europe 274: Now as Breitmann vas a vaitin / Among some demi reps, / Ascensionem expectans, / To see dem glime de steps.
1882		Bristol Magpie 7 Dec. 3/1: Let some foreign princess just give us the tip, / Or if not a princess some mad ‘demi-rip’.
1882		Sydney Sl. Dict. (2 edn) 3: Demirep - A courtezan. Contraction of ‘demi-monde’ reputation.
1883		Sun (NY) 20 May 2/7: The [opium] joints [...] had few regular frequenters, except sporting men, crooks [...] and all kinds of demireps.
1888–94		‘Walter’ My Secret Life (1966) VII 1388: Why with this feeling I sought Cyprians, demireps, sluts, and strumpets, which I have done, I cannot explain.
1890		H. Nisbet ‘Bail Up!’ 218: The dirty loafer or shabby demirep besides the silk skirt or dress-coat.
1900		P. White West End 346: Poor Sir John! Now he has a ‘demirep’ for a daughter-in-law.
1912		T.W.H. Crosland The First Stone 28: I may seem to belong / Not to the smirking fops / And sexless demireps [...] But to the company / Of the untroubled saints.
1926		Wood & Goddard Dict. Amer. Sl.
1940		R. Service ‘The Ballad of Touch-the-Button Nell’ in Bar Room Ballads (1978) 623: A whispered ‘Come,’ the skirl of some hell-raking demirep.
1966		Trimble 5000 Adult Sex Words and Phrases.
1976		P. Conroy Great Santini (1977) 504: I am a damirep [sic]. A very flighty woman.
1999		C. Dexter Remorseful Day (2000) 101: She’d be ‘Debbie Repp’, then; and that would be too close to ‘demi-rep’.