“Where y’ at?” or “Where yat?” is a popular New Orleans greeting, meaning “Where are you at?” or “How are you?” People who speak in this “Yat” dialect have themselves been called “Yats.”
 
“Where y’at, Rock?” was printed in the New Orleans (LA) Item on March 1, 1954. “And where else (but New Orleans—ed.) find people who bid you ‘good night’ before you leave and ask you ‘Where y’ at?’ while you are in plain sight?” was printed in The Times-Picayune (New Orleans, LA) on September 2, 1958. ‘Hopefully, “Where y’at, Cap?’ will never fade from Crescent City patois” was printed in The Times-Picayune on July 6, 1963.
   
“‘Where yat? is Chicagoese for ‘Where are you at?’” was printed in The Evening Sun (Baltimore, MD) on September 6, 1961.
   
“Yat,” as a noun for the language and the people who speak it, became widely used in the 1980s.
 
   
Wikipedia: New Orleans English
New Orleans English is American English native to the city of New Orleans and its metropolitan area.
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Often, the term “Yat” refers particularly to the New Orleans accents that are “strongest” or most especially reminiscent of a working-class New York City accent, though others use the term as a regional marker, to define the speech heard in certain parts of the city and its inner suburbs. Used in these narrower senses, Yat is simply one of many sub-dialects of New Orleans. The word comes from the common use of the local greeting, “Where y’at?” or “Where are you at (i.e. in life)?”, which is a way of asking, “How are you?”
     
1 March 1954, New Orleans (LA) Item, Industrial Weekly, pg. 1, col. 1:
Where Y’At,
Rock?
“Where y’at, Rock?”
 
12 July 1954, New Orleans (LA) Item, pg. 5, col. 3:
Where Y’at, Catalog?
 
27 July 1955, New Orleans (LA) Item, Industrial Weekly, pg. 2, col. 3:
Service Industry Of The Week
Supplies Parts In Parcels
Where y’at, Jack?
       
2 September 1958, The Times-Picayune (New Orleans, LA), “Views of Readers,” pg. 14, col. 7:
And where else (but New Orleans—ed.) find people who bid you “good night” before you leave and ask you “Where y’ at?” while you are in plain sight?
TAFT J. FABIAN.
     
6 September 1961, The Evening Sun (Baltimore, MD),  “Mr. Peep’s Diary: Chicahgah Claims A Dialect,” pg. 39, col. 1L
“Where yat?” is Chicagoese for “Where are you at?”
   
5 May 1962, The Times-Picayune (New Orleans, LA), “Kennedy Enjoys Children Most During Stay in N.O.” by Podine Schoenberger, sec. 1, pg. 23, col. 1:
One sign said, “Where y’at Jack.”
 
26 August 1962, The Times-Picayune (New Orleans, LA), “They Put Wrong Words in Mouths of N.O. People” by Albert Goldstein, sec. 3, pg. 12, cols. 6, 8:
It’s the sergeant on the other end of the line, and the cop says: ‘Where are you telephoning from, Sergeant?” I say no New Orleans policeman would ever put it that way. He’d say: ‘Where y’at, Sarge?”
(...)
There is such a thing as New Orleansese. But the fiction-writing fraternity apparently hasn’t found out about it,
   
6 July 1963, The Time-Picayune (New Orleans, LA), “‘Tiger,’ ‘Skeeter,’ ‘Sarge,’ “Cap” Banned from Police Department” by Art Roane, sec. 1, pg. 4, col. 5:
Hopefully, “Where y’at, Cap?” will never fade from Crescent City patois.
 
20 February 1964, The Times-Picayune (New Orleans, LA), “Albert’s Noo Orleans” by Albert Goldstein, sec. 1, pg. 6, col. 6:
Joe nodded to the crew cut and said “Ha-ya?” The man nodded back and said “Where y’at?”
   
25 February 1967, The Louisiana Weekly (New Orleans, LA), “Dig Me!” by Joe Emery, sec. 1, pg. 7, col. 1:
WHAT’ YAT
   
13 April 1969, The Times-Picayune (New Orleans, LA), “Bright Talk,” Dixie Roto Magazine, pg. 18, col. 3:
Where Y’at, Cap?
 
2 October 1969, The Times-Picayune (New Orleans, LA), “Remoulade: ‘New Or-le-ana’ Is Seen in Cab Palaver” by Howard Jacobs, sec. 1, pg. 13, col. 1:
YOU’VE HEARD of “a bit of Americana,” and here’s “a bit of New Or-le-ana,” if we may coin a phrase. Fellow we know hailed a cab downtown Wednesday, and hadn’t gone a block before this conversation ensued between the cabbie and his dispatcher over the two-way radio.
 
Dispatcher—“Let me have your whereabouts.”
Driver—“What’s that?”
Dispatcher—“I want to know your approximate location.”
Driver—“Run that back again, willya?”
Dispatcher—“WHERE YAT?”
Driver (relieved)—“Oh, why diddin’ you say so in the first place? I’m in the commercial.”
 
31 July 1972, The Times-Picayune (New Orleans, LA), “Live! on Half Shell! Oysters!” by Don Hughes,  sec. 2, pg. 11, col. 6:
An oyster sauce since then has gained, quite justifiably, his place in the record books of sages, gourmets, bayou Cajuns, New Orleans Irish Channel Bairds, Ninth Ward “Where Yats” and anybody else who can garner up enough nerve to put that first gluey bivalve into his mouth and swallow it, while simultaneously proclaiming “Gee, that was good.”
 
23 February 1974, Daily World (New York, NY), “On the docks (of New Orleans—ed.) it’s blood, sweat and fears” by David Brown, pg. M-2, col. 1:
“Where y’at, babe? You working?”
 
12 March 1975, The States-Item (New Orleans, LA), “Metropolitan View” by Allan Katz, pg. A-7, col. 1:
He is especially fluent in “Yat,” as in “Where yat,” the local dialect that makes juries here feel warm and comfortable.
 
4 January 1976, The Times-Picayune (New Orleans, LA), “‘Ja’ to Some Films, ‘Nein’ to Others” by Frank Gagnard, sec. 2, pg. 8, col. 5:
As one who suffers when a community theater tries to dress up Noel Coward with broad vowel sounds, and comes out with equivalents of “Where yat, bloke?,” I find this a relief.
       
Google Books
The Dolphin Guide to New Orleans
By Carolyn Kolb
Garden City, NY: Dolphin Books
1984
Pg. 131:
The harsh, twangy “Brooklynese” you hear is the New Orleans native accent. Locals refer to people who speak this way as “yats.” This is because “Where yat” (“where you at”) is a New Orleans greeting. “Where yat, yuh muthah” is another form.
 
OCLC WorldCat record
New Orleans talkin’ : a guide to yat, creole, and some cajun
Author: Justin G T Lemotte; Maurice C Willems
Publisher: New Orleans, LA : The Channel Press, 1986, ©1985.
Edition/Format:   Print book : English
     
11 September 1988, New York (NY) Times, “On Language: Rot at the Top” by William Safire, pg. A24:
People who talk Cajun-style call themselves Yats, derived from ‘‘Where y’at?’’ (short for ‘‘Where are you at?’‘).
 
OCLC WorldCat record
New Orleans neighborhood talk : examining the original dialects of the New Orleans Ninth Ward neighborhood
Author: Linda DePascual; Jean Greenfield; Susan Miller; Barbara Molnar; Christye Robley; All authors
Publisher: New Orleans : Loyola University of New Orleans, ©1994.
Edition/Format:   Print book : English
Contents:
Printed word of Yat—
Mapping the neighborhoods—
Social origins of the Irish Channel—
Social origins of the Ninth Ward—
Attitudes toward Yat dialect speakers in New Orleans—
What is available on Yat: research of local libraries and archives in New Orleans
 
OCLC WorldCat record
Where y’at. : New Orleans’ monthly entertainment magazine.
Publisher: New Orleans, La. : Where y’at magazine.
Edition/Format:   Journal, magazine : Periodical : English
(1998-2012—ed.)
 
OCLC WorldCat record
An application of accommodation theory : a study of convergence to standard New Orleans English and Yat English
Author: Bernard J Lara
Publisher: 2000.
Dissertation: B.A. University of New Orleans 2000
Edition/Format:   Thesis/dissertation : Thesis/dissertation : Manuscript   Archival Material : English
 
OCLC WorldCat record
The Authenticity of Yat: A R`eal’ New Orleans Dialect
Author: F Coles
Edition/Format: Article Article : English
Publication: SOUTHERN JOURNAL OF LINGUISTICS, 25, no. 1/2, (2001): 74-86
 
OCLC WorldCat record
Yeah, this is New Orleans : ware yat, Vince!
Author: Joe Loré
Publisher: San Jose, Calif. : Writers Club Press, ©2002.
Edition/Format:   Print book : Fiction : English
 
OCLC WorldCat record
Boudreaux’s Cajun party guide = Guide de partie de Cajun
Author: Larry Boudreaux
Publisher: Baton Rouge, LA : Boudreaux Cajun General Store, ©2003.
Edition/Format:   Print book : English
Summary:
This guide to Cajun entertaining includes 15 themes for parties including “cochon de lait” and “crawfish boil”. The book includes: recipes, suggested music, games, contests, and jokes. It also has instructions for “Bouree” (card game), directions to make a Cajun microwave, a dictionary of Cajun and New Orleans Yat words, festivals, and other miscellaneous Louisiana customs.
 
OCLC WorldCat record
The joy of Y’at Catholicism
Author: Earl J Higgins
Publisher: Gretna, La. : Pelican Pub. Co., 2007.
Edition/Format:   Print book : English
Summary:
“New Orleans culture is a fusion of secular and holy. From the earliest days of the community founded on the banks of the Mississippi River, the Catholic faith has been an influence on, and inspiration for, daily life. To be sure, religious rites such as weddings, funerals, and feast day festivals transpire elsewhere in the country. In New Orleans, however, they are celebrated with a zeal and verve that speaks to the uniqueness of the community”—Publisher website (September 2007).
     
Google Books
DK Eyewitness Travel Guide: New Orleans
By Marilyn Gallagher
New York, NY: DK Pub.
2008
Pg. 248:
where y’at? how are you?
   
Urban Dictionary
Y’at
Slang term for a New Orleans native. The term is specifically used to describe residents of Orleans, Jefferson, and St. Bernard parishes, and is exclusive to the area. For natives, the term is most generally used to identify members of the Westbank region of New Orleans including residents of: Algiers, Terrytown, Gretna, Harvey, Marrero, Westwego, Avondale, Lafitte, and Belle Chasse.
(...)
by RyfromNola December 23, 2010
 
OCLC WorldCat record
The YAT language of New Orleans, the who dat nation : the true story—how it all began
Author: Ray Canatella
Publisher: Bloomington : iUniverse, ©2011.
Edition/Format:   Print book : English
 
OCLC WorldCat record
Yat wit : chicken gumbo for the New Orleans soul
Author: Yvonne Spear Perret
Publisher: Gretna : Pelican Pub. Co., 2011.
Edition/Format:   Print book : English
Summary:
“From the dilemma of deciding who gets the third beignet to dodging unyielding streetcars and suggestions for recycling Mardi Gras beads, this collection of humorous vignettes celebrates the quirks and perks of living in New Orleans. The book includes such topics as the life lessons learned from a crawfish boil and the proper etiquette for eating a po-boy and poaching ladders during parade season. Locals—and those who just love the city—will laugh out loud at Yvonne Spear Perret’s charm, which is cleverly crafted into each essay”—Page 4 of cover.
 
OCLC WorldCat record
The adventures of Yat and Dat : Superdome!
Author: Nancy Parker; Spencer Bradford; Ampersand, Inc. (Chicago, Ill.)
Publisher: Chicago, Ill. : New Orleans, La. : Ampersand, Inc., ©2013.
Edition/Format:   Print book : Fiction : Juvenile audience : English
Summary:
The curious birds, Yat and Dat, leave their Marigny tree top home and fly to the Superdome where they hope to watch “Dirty Birds” play the New Orleans Saints. They can’t believe that birds play football on that big Superdome floor. They swoop into a gate and what happens inside couldn’t be more exciting!
 
OCLC WorldCat record
Where y’at, Baby Jack? : a hide-and-seek adventure New Orleans style!
Author: Lisa Merkle; Tim Lattie
Publisher: Gretna : Pelican Publishing Company, 2015.
Edition/Format:   Print book : Fiction : Primary school : English
Summary:
The reader is invited to find the king cake baby as he plays a game of hide and seek in and around New Orleans. Includes author’s note on the traditions and culture of the king cake.
 
OCLC WorldCat record
New Orleans neighborhoods : a cultural guide
Author: Maggy Baccinelli
Publisher: Charleston, SC : The History Press, 2015.
Edition/Format:   Print book : English
Summary:
“Where y’at? In New Orleans, this simple question can yield hundreds of answers. People on the same block might say that they live in Pigeon Town, Pension Town or Carrollton, but they have surely all danced together at the neighborhood’s Easter Sunday second-line. Did you know that gospel queen Mahalia Jackson grew up singing in a little pink church in the Black Pearl or that Treme is the oldest African American neighborhood in the country? In an exploration that weaves together history, culture and resident stories, Maggy Baccinelli captures New Orleans’ neighborhood identities from the Mississippi River to Lake Pontchartrain”—Publisher description.
 
OCLC WorldCat record
Ain’t Dere No More: New Orleans Language and Local Nostalgia in Vic & Nat’ly Comics
Author: Katie Carmichael Affiliation: Department of English Virginia Tech; Nathalie Dajko Affiliation: Department of Anthropology, , Tulane University
Edition/Format: Article Article : English
Publication: Journal of Linguistic Anthropology, v26 n3 (December 2016): 234-258
Summary:
As “local,” “authentic,” “working class,” “white,” “urban,” and “salt of the earth” characters, Vic and Nat’ly, the protagonists of Bunny Matthews’s classic comic strip, embody all of the stereotypes of a New Orleans-based “Yat” identity. In this paper, we examine written representations of Yat English in Vic & Nat’ly strips, analyzing these results in comparison with current linguistic data from actual New Orleans English speakers and contextualizing our interpretation in terms of social and historical changes within post-Katrina New Orleans.