A cheap restaurant or diner, especially one that serves simple or low-quality food; slang for a modest eating establishment.
From bean (Old English 'bean') combined with the suffix -ery. The term became slang in 19th-century America, likely because beans were an inexpensive staple food of poor diners.
The shift from 'beanery' (a cheap food place) to 'greasy spoon' to 'diner' shows how Americans keep inventing new slang for humble restaurants as words get too polite or old-fashioned!
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