Hash is a culinary dish consisting of chopped up meat, potatoes, and onions fried. The name is derived from French: hacher, meaning "to chop". It originated as a way to use up leftovers. By the 1860s, a cheap restaurant was called a “hash house” or “hashery.” 
Canned corned beef hash became especially popular in countries such as Britain, France, and the United States, during and after the Second World War as rationing limited the availability of fresh meat.
High-end restaurants offer sophisticated hash dishes on their menus.  Modern preparations can be made with unconventional ingredients such as lamb, fish, venison, turkey, chicken, shrimp, or steak.
"Hash" of many forms was part of the American diet since at least the 18th century, as is attested by the availability of numerous recipes and the existence of many "hash houses" named after the dish. In the United States, September 27 is "National Corned Beef Hash Day."
Classic American corned beef hash originated in the New England region of the United States as a way to use up the leftovers from a traditional boiled dinner of beef, cabbage, potatoes, and onions. A red flannel hash is made with beets instead of potatoes. You can also find salt cod hash or fish hash in New England.
Corned beef and cabbage dinners is an Irish-American tradition from the 1800's that is now commonly observed across the United States on St. Patrick's Day. Corned beef hash is also commonly served on St. Patrick's Day, as well as around American Thanksgiving and Christmas.
In the Midwest it was common to bind a hash together with a white sauce thickened with flour.
Alternatively, in the southern United States, the term "hash" may refer to two dishes:
- a Southern traditional blend of leftover pork from a barbecue mixed with barbecue sauce and served over rice. This is a common side dish at barbecue restaurants and pig pickin's notably in South Carolina and Georgia.
- In Texas, a thick stew made up of pork, chicken and beef, traditionally seasoned with salt and pepper and other spices, is reduced overnight over an open flame in an iron washpot or hashpot.
As early as the 14th century, English people were making hache or hachy. According to cookbook author Steven Raichlen, "The English diarist Samuel Pepys waxed grandiloquent about a rabbit hash he savored in 1662", and during World War I, American GIs consumed a steady diet of corned beef hash, which they christened “corned Willie.”
In Denmark, hash is known in Danish as "biksemad" (roughly translated, "tossed together food"), and it is a traditional leftover dish usually served with a fried egg, worcestershire sauce, pickled red beet slices and ketchup or Bearnaise sauce. The meat is usually pork, and the mixture is not mashed together into a paste, but rather the ingredients are coarsely diced and readily discernible in their cooked form.
In Sweden, there is a version of hash called pyttipanna and in Finland, pyttipannu and Norway, pyttipanne. It is similar to the Danish version. The Swedish variety Pytt Bellman calls specifically for beef instead of other meats and adding cream to the hash. It is named after Sweden's 18th century national poet Carl Michael Bellman.
In Austria and perhaps more specifically Tyrol, there exists a similar dish called "Gröstl", usually consisting of chopped leftover meats (often being pork sausage), potato and onions fried with herbs (typically marjoram and parsley) and then served topped with a fried egg.
In Slovenia it is called ''haše'' and very often used as a spaghetti sauce. It is made out of minced pork and veal meat, potato sauce, onion, garlic, flour and spices.
In Spanish, Portuguese and Latin American cuisines, there is a similar dish called picadillo (Spanish) or carne moída (Portuguese). It is made with ground meat (usually beef), tomatoes (tomato sauce may be used as a substitute), vegetables and spices that vary by region (the Portuguese and Brazilian version is generally carne moída refogada, very heavy on garlic, in the form of an aioli sofrito called refogado, and often also heavy on onion and bell peppers). It is often served with rice (it can be fried in aioli sofrito if those who will eat have a strong fondness for garlic), as well as okra, in the form of quiabo refogado—okra fried in an aioli sofrito, just as the hash itself and the collard greens used in feijoada—, in Brazil, there constituting a staple) or used as a filling in dishes such as tacos, tostadas, or as a regular breakfast hash with eggs and tortillas (not in Brazil and Portugal). In Brazil and Portugal, it is used as bolognese sauce for pasta, and also used as a filling for pancake rolls, pastel (Brazilian pastry empanada), empadão and others (not with okra as it is far too perishable to be used in a fill for fast food and its consumption together with wheat flour-based foods often does not fit cultural tastes). The name comes from the West Iberian (Spanish, Leonese and Portuguese) infinitive verb picar, which means "to mince" or "to chop".
- Online Etymology Dictionary. Retrieved on 2012-09-28.
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- WW2 People's War – Good Comes From Evil: Part 1. BBC. Retrieved on 2011-04-09.
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- "The King of the Concoctions". Chicago Tribune. 1988-12-25. Retrieved April 7, 2012.No Matter How You Chop It, Hash Makes Leftovers Into A Feast. William Rice, Chicago Tribune
- Hess, Mrs. Glasse ; in facsimile, with historical notes by Karen (1998). The art of cookery made plain and easy. Bedford, Mass.: Applewood Books. pp. 63, 73, 79. ISBN 1-55709-462-4.
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- columnist, Text by William Rice, SUNDAY`s food and wine. "THE KING OF THE CONCOCTIONS". chicagotribune.com. Retrieved 2019-09-12.
- Harding, Paul; Mark Elliott; Steve Kokker; Tom Masters (2007). Scandinavian Europe. Lonely Planet. ISBN 978-1-74104-553-6.
- Picadillo | Define Picadillo at Dictionary.com. Dictionary.reference.com. Retrieved on 2011-04-09.
- , Recipe for labskaus at About.com
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