Green’s Dictionary of Slang

1. the head, esp. in boxing use.

1832

Egan Bk of Sports 200: Sam’s nob had also been in pepper alley; and his upper crust was rather changed.

2. a hat.

1827		‘The Will’ in Egan Anecdotes of the Turf, the Chase etc. 75: I give to Bob Logic, when I’m in the dust, / My new lilly topper and best upper crust.
1830		Egan Finish to the Adventures of Tom and Jerry (1889) 309: I give and bequeath unto my friend, Jerry Hawthorn, Esq., my tile, my castor, my topper, my upper-crust, my pimple coverer, otherwise my hat.

3. the social élite, the aristocracy.

1823		‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc. 187: One who lords it over others, is Mister Upper-crust.
1845		D. Corcoran Pickings from N.O. Picayune (1847) 165: William Weithman, a loafer of the upper crust.
1853		Woodville Republican (MS) 1 Feb. 1/2: He is de ‘Upper Crust’ – / Ob all de well-born darkies.
1861		Hills & Plains 2 82: Little forms of writing [...] which the experienced strata of the upper crust find it most satisfactory to correspond with the lower.
1866		Charleston Dly News (SC) 28 Dec. 2/1: Among the ‘upper crust’ of darkeydom.
1869		Man about Town 30 Oct. 57/3: [P]ortents shadowing forth future upheavals and disruptions in the ‘upper crust’.
1872		Schele De Vere Americanisms 646: Upper Crust, Upper Ten Thousand, and Uppertendom, with a host of similar crudities, owe their origin to the unfortunate taste of a writer of great ability and well-earned popularity, N. P. Willis.
1880		Bulletin (Sydney) 10 July 13/2: Some ladies belonging to the ‘upper crust’ in Sydney are to be seen incog., early in the fore noon [etc].
1882		G.A. Sala in Living London (1883) Mar. 80: He is known only as a comedian of rare and precious qualities [...] moving us now to mirth in The Upper Crust, and now to tears in Uncle Dick’s Darling.
1890		Bulletin (Sydney) 9 Aug. 14/3: And now the upper-crust has any amount of small scandal to amuse afternoon tea’ers with.
1898		F. Dumont Dumont’s Joke Book 99: Only poor people eat punkin pi – and that’s right for punkin pi was never made for the upper crust.
1901		Manchester Courier 16 Mar. 12/2: ‘He claims to be very swell, but he’s rather ordinary, isn’t he?’ ‘Yes [...] just between the upper crust and the under-bred’.
1902		W.A. Sun. Times (Perth) 2 Feb. 1/1: The play's ‘enthusiastic reception’ by Bungaree’s ‘upper crust’ was more Duff than puff.
1905		‘Central Connecticut Word-List’ in DN III:i 23: upper crust, n. phr. The aristocracy.
1912		Truth (Sydney) 8 Dec. 6/6: They are runnin’ of their steamboat / Are that same ole huppercrust. / At a pace which, safe as houses, / Some day will their boilers bust.
1927		S.J. Perelman in Marschall That Old Gang o’ Mine (1984) 33: Coney Island [...] will always rank as the playground of the ‘upper crust.’.
1939		Charleston (WV) Daily Mail 29 Aug. 1/4: [advert] The Lowdown on the Uppercrust! Secrets of society playgirls.
1941		in G. Legman Limerick (1953) 191: There once was a handsome Haitian, / The luckiest dog in creation, / He worked for the rubber trust / Teaching the upper crust / The science of safe copulation.
1956		‘Charles Raven’ Und. Nights 102: How little Barney knew about the habits of the upper crust.
1972		Milner & Milner Black Players 247: Independent call girl with established book of regular tricks. Can move in any circles, including ‘upper crust.’.
1982		R. Dahl Revolting Rhymes n.p.: Ah, Piglet, you must never trust / Young ladies from the upper crust.
1990		R. Campbell Sweet La-La Land (1999) 180: Now the upper crust of La-La Land isn’t the same kind of crust as the crust in New York, Chicago or San Francisco.

4. any form of élite, e.g. criminal, but with no aristocratic implications.

1895		Truth (Sydney) 5 May 1/1: Dr Lea, the latrest victim of the tyranny prevalent among the ‘upper crust’ in Her Majesty’s Knavee.
1953		E. Hunter ‘Vicious Circle’ in Jungle Kids (1967) 26: After this one I’d be in the upper crust, one of the wheels.
1954		(con. 1940s) T.A.G. Hungerford Sowers of the Wind 154: Now the upper crust has gone [...] we can have some fun.