Definition: aristocracy, the upper class of society (used as noun or hyphenated as an adjective)
Origin: Upper crust is one of those phrases that has several plausible etymologies; even lexicographers disagree over the true origins of the term. When lexicographers begin duking it out over definitive etymologies, things get very interesting. The most repeated fallacy regarding “upper crust” can be found on various sites on the Internet and on the lips of tour guides of English manors. The lexicographers at phrases.org don’t mince words: “Advance within twenty yards of any English manor house that has mediaeval kitchens and you can’t avoid hearing that ‘upper crust was the superior, unburnt part of a loaf that was served to the gentry’… it may be true but there’s no documentary evidence to support it. This piece of folk wisdom is part of the collection of twaddle that has done more to spread false phrase etymologies than anything else.”
Apparently, respected lexicographer Robert Hendrickson stepped into this same puddle of twaddle in his monumental bible of phrase origins (Encyclopedia of Word and Phrase Origins), when he quotes John Russell’s “Book of Manners” (c. 1460): “Cut the upper crust [of the loaf] for your sovereign.” Hendrickson notes that Russell was referring to the custom of slicing the best part of the bread, the upper crust, to serve it to the ranking noble at the table.
Lexicographer John Ayto agrees with his colleagues at phrase.com: “The evidence [for the crust served to honored guests] is fairly tenuous.” What undermines the “sliced bread” explanation is that the phrase did not become a figurative term for the aristocracy until more than three and a half centuries later. John Badcock’s (yes, the irony of his name is not lost on astute readers) slang dictionary, titled “Slang: Dictionary of the Turf (1823),” includes this entry: “Upper-crust: one who lords it over others, is Mister Upper-crust.”
The more likely etymology, believe the second contingent of lexicographers, is that “upper crust” is connected to the meaning of “top” referring to the Earth’s [upper] crust or a person’s head that, in the early 1800s, was figuratively called the “upper crust.”
For further reading: Brewer’s Dictionary of Phrase & Fable by John Ayto, Weidenfeld & Nicolson (2005)
The Facts on File Encyclopedia of Word and Phrase Origins by Robert Hendrickson, Facts on File (2008)