Where did the term who dat come from?
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Wheat type of speaking did the term who dat originally come from?
African-American Vernacular English (AAVE) and lower middle- and working-class white pronunciation of the question "who's that?"
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Where did the term who dat come from and first publish?
New Orleans Daily Picayune article
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Where did the term who dat used, with respect to sports, come from?
Patterson High School Southern University Jaguars St. Augustine High School
Who Dat?
https://en.wikipedia.org/wiki/Who%20Dat%3F
The earliest documented use of the phrase can be found in a July 30, 1852 New Orleans Daily Picayune article.

The chant of "Who Dat?" originated in minstrel shows and vaudeville acts of the late 19th and early 20th centuries and was taken up by jazz and big band performers in the 1920s and '30s.[4]
Who Dat? Origins
"Who Dat" became part of a chant for fans cheering on their favorite team. It has been debated exactly where it started, but some claim it began with Southern University Jaguars fans either in the late 1960s or early 1970s and went "Who dat talkin' 'bout beatin' dem Jags?"[11] Another claim is that it was connected with St. Augustine High School, a historically African-American all-boys Catholic high school in New Orleans.
Who Dat? Origins of the "Who Dat?" chant
The term "who dat" is a part of African-American Vernacular English (AAVE) and lower middle- and working-class white pronunciation of the question "who's that?" The earliest documented use of the phrase can be found in a July 30, 1852 New Orleans Daily Picayune article, while the chant was first found in minstrel shows and vaudeville acts in the late nineteenth and early twentieth centuries. There are multiple claims to the origin of the term "who dat" with respect to sports. Some claim it began with the Southern University Jaguars, but some claim is that it was connected with St. Augustine High School, a historically African-American all-boys Catholic high school in New Orleans.