Entry in progress—B.P.
 
Wikipedia: Kosher foods
Kosher foods are those that conform to the rules of Jewish religion. These rules form the main aspect of kashrut, Jewish dietary laws.
 
Reasons for food being non-kosher include the presence of ingredients derived from non-kosher animals or from kosher animals that were not properly slaughtered, a mixture of meat and milk, wine or grape juice (or their derivatives) produced by only Rabbi, the use of produce from Israel that has not been tithed, or even the use of cooking utensils and machinery which had previously been used for non-kosher food. Kosher is eaten mainly by Orthodox Jews but other Jews are not so specific. The phrase kosher may also be used to refer to the diet of the Jewish religion.
     
Merriam-Webster Dictionary
Main Entry: 1ko·sher
Pronunciation: \ˈkō-shər\
Function: adjective
Etymology: Yiddish, from Hebrew kāshēr fit, proper
Date: 1851
1 a: sanctioned by Jewish law ; especially : ritually fit for use “kosher meat” b: selling or serving food ritually fit according to Jewish law “a kosher restaurant”
2: being proper, acceptable, or satisfactory “made sure the deal was kosher”
 
(Oxford English Dictionary)
kosher, a. (n.)
[Heb. kshr right.]
adj. a. Right, good; applied to meat and other food prepared according to the Jewish law.
1851 MAYHEW Lond. Labour (1861) II. 121 The meat killed according to the Jewish law is known as ‘Coshar’. 1864 Times 4 Aug. Advt., They will be supplied with Kosher meat of the best quality.
1892 ZANGWILL Childr. Ghetto vi. (1893) 66 The butter and cheese were equally kosher, coming straight from Hebrew Hollanders.
1892 M. WILLIAMS Round London (1893) 107 We [Jews] get our kosher meat killed in our own way by our co-religionists according to the law of Moses.
1934 J. BROPHY Waterfront i. 23 To cook food in the prescribed kosher manner.
1959 Hotel Managem. & Restaurant Trade Jrnl. Feb. 28/2 Only kosher meals are served on El Al aircraft.
1971 Guardian 14 Oct. 11/2 The artificial meat business has a very good-going trade already in Kosher bacon made from soya beans.
1973 Jewish Chron. 19 Jan. 1/5 The Kissingers will also be given kosher food.
   
b. Hence of shops, houses, etc., where such food is sold or used. Also kosher butcher.
1889 N. & Q. 7th Ser. VIII. 85 The defendant kept a ‘kosher’ shop.
1892 ZANGWILL Childr. Ghetto I. 250, I should have to keep a kosher house, or look how people would talk.
1932 KIPLING Limits & Renewals 359, I had a whole tin of salmon once from a kosher butcher.
1973 Guardian 16 June 3/6 The last kosher butcher left for Israel.
   
c. Correct, genuine, legitimate. colloq.
1896 FARMER & HENLEY Slang IV. 135/1 Kosh (or Kosher)... Adj. (common).—Fair; square.
1924 Cosmopolitan Nov. 104/2 It don’t sound kosher to me!
1930 D. RUNYON in Sat. Even. Post 13 Sept. 7/3 ‘Everything is very Kosher,’ Harry the Horse says. ‘You need not be afraid of anything whatever. We have a business proposition.’
1930 Amer. Mercury Dec. 456/2 Listen shamus, you got me wrong. I’m strictly kosher.
1953 H. MILLER Plexus iv. 164, I made little or no effort to keep up with the others, it being no concern of mine what went on in this realm of make believe. All I felt called upon to do was to keep a straight face and pretend that everything was Kosher.
1959 C. MACINNES Absolute Beginners 80 It’s so as to play down the queer thing in our country, and hide it behind the kosher game. Ibid. 157 It’s all very well sneering at universities..but really and truly, it would be wonderful to have a bit of kosher education.
1961 L. GRIBBLE Wantons die Hard iv. 48 ‘No financial irregularities?’ ‘Strictly kosher… It’s so good it stinks.’
1966 T. PYNCHON Crying of Lot 49 iii. 60 They got the contracts. All drawn up in most kosher fashion, Manfred.
 
February 1847, The Occident and American Jewish Advocate, pg. 553:
On the subject of Shochetim, and the sale of Kosher meats, a committee of competent men has benn selected by the united boards.
 
30 March 1855,

(Cincinnati, OH), pg. 304, col 1 ad:
NEW ENGLAND HOUSE,
Hartford, Conn.
THE UNDERSIGNED RESPECTFULLY calls the attention of his friends and the ravelling community at large, to his commodious and well managed hotel, No. 5, Front street, Hartford, Conn.  The best accommodations and a first rate kosher table will be found at any time.
SIMON SELLING, Proprietor
 
9 November 1866, The Israelite (CIncinnati, OH), pg. 6, col. 4 ad:
M. BERLINGER’S
KOSHER BOARDING HOUSE AND RESTAURANT
No. 13 Lodge Street between 5th and 6th
CINCINNATI, O.
Meals at all hours of the Day.
 
15 February 1867, The Israelite (Cincinnati, OH), pg. 7, col. 3:
G. SELIGMAN begs to inform you that he will remove from his present premises, No. 254 Broadway, New York
To the BASEMENT
No. 20 White Street, Near Church,
And open on the 1st of FEBRUARY his well known
(“Kosher” in Hebrew—ed.)
RESTAURANT
Where he will continue to serve dinners (and a cup of coffee) for fifty cents.  Breakfast and supper a la carte.
   
G. Seligman begs to return thanks for past favors, and solicits a continuance of the same at his new and spacious premises, where he will endeavor to do still better.
 
1 July 1881, The Jewish Chronicle (London), pg. 4, col. 1:
WINE MERCHANTS.
JAMESON & SONS, 85 Mansell Street, E.  Importers of (“Kosher” in Hebrew—ed.) Wines.
   
OCLC WorldCat record
Directory of kosher hotels, boarding houses and restaurants in the United States.
by United Synagogue of America.
Type:  Book; English
Publisher: New York, 1919.
   
October 1954, Jewish Social Studies, vol. 16, no. 4, pg. 345:
The Jewish butchers of Prague were the first trade group to organize a guild of their own. The axact year of its founding is unknown, but the guild’s key bears the date 1620. Engraved on the key are the names of the two guild wardens, Solomon Wilhartitz and Elias Nefele, and of thirteen guild members. At the base of the key is the representation of a lion rampant, the
device of the city of Prague, holding between its forepaws a butcher’s axe inscribed with the Hebrew word kosher.*
 
*Spiegel, Kathe, “Die Prager Juden zur Zeit des dressigjahrigen Kreiges,” in Die Juden in Prag (Prague 1927) p. 130, 180.
(HEBREW word “kosher”—ed.)