This thread inspired me to actually read a book that I bought from a used book store some years ago Martin William's Jazz Masters of New Orleans (New York;The Macmillian Company, 1967.

Here is an excerpt from that book's introduction:

"As any history of the music will tell us, jazz started in New Orleans.

Surely it must have, for in 1917 a group of musicians from New Orleans suddenly found themselves a success in New York City, playing a music they had learned there. On their records, they were called "Dixie Jass Band" and later "Original Dixieland Jazz Band." And a few years earlier, it turns out, the Original Creole Orchestra, from New Orleans, had been playing the same style on the Orpheum Theater circuit"...

p. xi

-snip-

While reading this book, I finally "got" that the word "original" in the name "Original Dixieland Jazz Band" was added to promote the tale that these musicians were the original creators of the music called jass/jazz.

..."the [Nick] LaRocca group, which was by now appearing at the Casino Gardens as the Dixie Jass Band.

Soon after, a booker approached Brown for another New York job, but his group had dissolved by then and he recommended the LaRocca group. Thus on January 15 the "Dixie Jasz (sic) Band" opened in a club called the Paradise in New York...At first business was hardly sensational. Apparently, the management had trouble persuading the public that the music was supposed to be danced to, but it hung on. It had two other ballrooms in the building offering waltzes which helped to pay the freight. And by the end of the year nightclubbers were flocking to Reinsenweber's third floor; the Paradise club had become fashionably "in," and had raised its prices and the band's pay. Soon an electric sign outside read "The Original Dixieland Band-Creators of Jazz."
pp 29-30.


-snip-

Author Martin William also asserts that the ODJB frequently "borrowed" from other bands and musicians.

"The group was first recorded by Columbia, then Victor, then Aeolian, but the Victory record of Livery Stable Blues and Dixie Jass Band One Step (later Original Dixieland One-Step) was the seller. The former title was apparently responsible for its huge success. It featured rooster sounds from Shields' clarinet, cow moos from Edwards, and horse whinneys ( out of Freddy Keppard's lighter moments, the old timer's say) from Ka Rocca. The public thought the music was hilarious. And so, in a sense it was. But to any who knew its sources, the effect of its reception and popularity must have painfully ironic. And it's Keppard's Creole Band, by the way, that Jelly Roll Morton as the direct origin of the O.D.J.B.'s style.

The recordings put the O.D.J.B. repertory on wax. The tunes were each made up of several parts or strains, a form modeled on ragtime pieces, but played differently, and many of them, according to musicians still down home, borrowed from the repertory of the colored bands of New Orleans...

p. 30

This is from a foot note found on that same page:   

It might be further noted that the melody of Barnyard Blues or Livery Stable Blues is taken from Stephen Adam's hymn, The Holy City; that the first strain of Fidgity Feet echoes At a Georgia Cam[ Town Meeting (1897); the third stain of Dixieland One-Step echoes That Teasin' Rag (1909); that the main strain to At The Jazz Ball uses the chords to Shine On Harvest Moon; and that Tiger Rag has the same chords as Sousa's National Emblem March.