Consider this my own version of "Better Know an Opponent"
The infamous Urban Dictionary defines it thus:
St. Louis Meaning: white trash of the worst kind. Also used as an adjective to describe anything several notches below your own perceived sophistication. Dates back to a strike that occurred in St. Louis in the 30's. During this strike, scab workers from Indiana were brought in to fill in for strikers. The perjorative hoosier stems from the St. Louis workers' lack of appreciation for this.
Wikilou (a wikipedia-like site about St. Louis) defines it so:
In a nutshell, it's the St. Louis term for white trash or redneck. Also similar to "hesher" which is more common out west. There actually is a link to Indiana hoosiers in the way the term became known as being derogatory. But exactly when that happened is up for debate.
The Indiana Historical Bureau suggests:
But where did Hoosier come from? What is its origin? We know that it came into general usage in the 1830s. John Finley of Richmond wrote a poem, "The Hoosier's Nest," which was used as the "Carrier's Address" of the Indianapolis Journal, Jan. 1, 1833. It was widely copied throughout the country and even abroad. Finley originally wrote Hoosier as "Hoosher." Apparently the poet felt that it was sufficiently familiar to be understandable to his readers. A few days later, on January 8, 1833, at the Jackson Day dinner at Indianapolis, John W. Davis offered "The Hoosher State of Indiana" as a toast. And in August, former Indiana governor James B. Ray announced that he intended to publish a newspaper, The Hoosier, at Greencastle, Indiana.
A paper by Jeffrey Graf, of the University of Indiana, speculates:
The best evidence, however, suggests that "Hoosier" was a term of contempt and opprobrium common in the upland South and used to denote a rustic, a bumpkin, a countryman, a roughneck, a hick or an awkward, uncouth or unskilled fellow. Although the word's derogatory meaning has faded, it can still be heard in its original sense, albeit less frequently than its cousins "Cracker" and "Redneck."
From the South "Hoosier" moved north and westward with the people into the Ohio Valley, where it was applied at first to the presumably unsophisticated inhabitants of Southern Indiana. Later it expanded to include all residents of the state and gradually lost its original, potent connotation of coarseness in manners, appearance and intellect. As for the word itself, it probably derives from the Saxon word "hoo" meaning promontory or cliff or ridge or rise or hill. Jacob Piatt Dunn, a diligent scholar of the word, believes a Saxon beginning, and such a meaning survives in various place names in England. There is some sense in the notion, too, that those who applied the insult and those to whom it was applied (and who understood it) came primarily from British stock.
He later goes on to address how the word "Hoosier" and St. Louis intersect:
While "hoosier" may still be heard in areas of the south in its original, disparaging meaning of "uncouth rustic," the term seems to be slowly loosing currency. One important pocket of linguistic resistance, however, remains. Thomas E. Murray carefully analyzed the use of "hoosier" in St. Louis, Missouri, where it is the favorite epithet of abuse. "When asked what a Hoosier is," Murray writes, "St. Louisans readily list a number of defining characteristics, among which are 'lazy,' 'slow-moving,' 'derelict,' and 'irresponsible.'"
He continues, "Few epithets in St. Louis carry the pejorative connotations or the potential for eliciting negative responses that hoosier does." He conducted tests and interviews across lines of age and race and tabulated the results. He found the term ecumenically applied. He also noted the word was often used with a modifier, almost redundantly, as in "some damn Hoosier."
One thing I found that did sort of tie in with the Missouri
In the movie, a shop keeper states "He's a hoosier," much to the disgust of an elderly customer. The video below is short but MIZZOUfaninAZ pointed out to me there's more to from the film:
GRANDMA SARAH: Well, sir, we'll do without molasses. Anything from Missouri has a taint about it.
GRANDPA SAMUEL: Now, Grandma, you've got to tread lightly now we're here in Texas. Lots of nice elements from Missouri coming West.
GRANDMA SARAH: Never heard of nice things from Missouri coming West. And treading lightly is not my way. (To the shopkeeper) We're from Kansas. Jayhawkers, and proud of it.
SHOPKEEPER: I know how you feel. I'm a Hoosier, myself.
GRANDMA SARAH: Personally, I don't think much of Hoosiers neither.
However, perhaps the most ignorant thing I found in my investigation was this (emphasis mine):
I’m suspending that emotional boycott for this one game. I want the Hoosiers to beat the living hell out of the Missouri Tigers this Saturday night for a variety of reasons, but chief among them is the oddly haughty attitude people in the Show Me State display toward those from Indiana.
If you think the recent dust-up over the use of Redskins by the NFL team based in Washington DC shows an ugly side to how callous Americans are in depicting Native Americans, they have nothing on Missourians’ disdain for all things from Indiana.