Who dat? is an alternate pronunciation of the question "who's that?"
Recently, the phrase "who dat?" has become a chant of team support. It is most widely used by fans of the New Orleans Saints, an American football team. The entire chant is: "Who dat? Who dat? Who dat say dey gonna beat dem Saints?" "Who dat" may also be used as a noun, describing a Saints fan.
Origins
The earliest documented use of the phrase in Louisiana 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.
Early references to "who dat?" can be found in the 19th century in the poetry of Paul Laurence Dunbar, first in his poem "When Malindy Sings" and later in his lyrics to the song "Who Dat Say Chicken in dis Crowd," a featured song in Clorindy: The Origin of the Cakewalk, an "operetta" by Dunbar and Will Marion Cook that was first presented as part of E.E. Rice's 1898 show "Summer Nights". A common tag line in the days of Negro minstrel shows was: "Who dat?" answered by "Who dat say who dat?" Many different blackfaced gags played off that opening. Vaudeville performer Mantan Moreland was known for the routine. Another example is "Swing Wedding", a 1930s Harman-Ising cartoon musical, which caricatured Fats Waller, Cab Calloway, Bill "Bojangles" Robinson, Ethel Waters, and the Mills Brothers as frogs in a swamp performing minstrel show jokes and jazz tunes. The frogs repeatedly used the phrase "who dat?"
In the swing era, "who dat" chants back and forth between the band and the band leader or between the audience and the band were extemporaneous. That is, there was no one specific set of words except for the two magic ones.
"Who Dat?" lyrics from 1937:
Who dat up there who's dat down there
Who dat up there who dat well down there
Who's dat up there, sayin' who's dat down there
When I see you up there well who's dat down there
Who dat inside who's dat outside
Who's dat inside who dat well outside
Who's dat inside, singin' who's dat outside
When I see up there well who's dat out there
Button up your lip there big boy
Stop answerin' back
Give you a tip there big boy
Announce yourself jack
Who dat up there who's dat down there
Who dat up there who dat, well down there
Who's dat up there, singin' who's dat down there
When I see you up there you bum
Well who's dat down there
Who dat
Staged minstrel skits featured frightened African American characters saying "who dat" when they encountered a ghost, or someone imitating a ghost. Then, the "who dat"–"who dat say who dat" skit would play itself out. This skit was done frequently in short reels from the 1930s to 1950s and in some early TV shows too. Even the Marx Brothers had a "who dat" routine, which they included in their film A Day at the Races. "Who Dat Man? Why It's Gabriel!" Often, a ghost was called a "who dat." Metro-Goldwyn-Mayer's animated character Bosko once had such an encounter in a 1938 toon called "Lil Ol Bosko in Bagdad." In 1941 Butterfly McQueen infamously delivered what African American film historian Donald Bogle described as what "might be the most demeaning line ever uttered by a black in the movies" when she said, "Who dat say who dat when I say who dat?" in the movie Affectionately Yours.
"Who dat?" became a familiar joke with soldiers during World War II.
Back in WWII, U.S. fighter squadron pilots would often fly under radio silence. But things get lonely up there in the cockpit, so after a while there'd be a crackle of static as someone keyed his mike. Then a disembodied voice would reply, "Who dat?" An answer would come, "Who dat say who dat?" And another, "Who dat say who dat when ah say who dat?" After a few rounds of this, the squadron commander would grab his microphone and yell, "Cut it out, you guys!" A few moments of silence. Then... "Who dat?"
Origins of the "who dat?" chant
"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?" Another claim is that it was connected with St. Augustine High School, a historically African-American all-boys Catholic high school in New Orleans.