“Thou Swell”? Few song titles capture better the irreverence of this new style of musical (and verbal) expression. The tune comes from the 1927 musical A Connecticut Yankee, a story based on Mark Twain’s old book about a smart-talking American teaching King Arthur’s court how to modernize its ways based on U.S. values. But if the plot was an old one, the story was a perfect fit for the new American confidence of the late 1920s.

Yet something even more shocking than “Thou Swell” and “’S Wonderful” had now arrived on the music scene. This same period witnessed the mainstreaming of folk blues music from the poorest parts of the South. Paramount enjoyed huge sales with the raw guitar-and-vocal recordings of Blind Lemon Jefferson, and a host of other blues singers followed in his footsteps. But country music also hit a new stride during this 15-month period, with the first recordings of Jimmie Rodgers and the Carter Family Singers. Whether white or black, mainstream or outsider, Americans were embracing less polished forms of expression, seeing in them an authenticity that more sophisticated discourse lacked.

Newspapers also began to grasp the newfound popularity of American vernacular talk. In 1926, just as Hemingway was launching The Sun Also Rises, Will Rogers started producing a daily column for syndication. His homespun way of expression, presented under the title “Will Rogers Says” would eventually attract an audience of 40 million readers—making him one of the most influential commentators of his generation. Over the next two years, Rogers would tour the U.S. and Europe, with much of his appeal coming from his rule-breaking approach to language, which found him mixing slang, cowboy talk, Southern dialect, and puns in a unique hybrid.

The days of the grand style, whether in books or spoken language, were now over. Movies, music, and fiction all embraced the new idiom with enthusiasm. It was only a matter of time before the rest of the world jumped on the bandwagon. When Louis Armstrong gave a command performance at Buckingham Palace in 1932, he shook up protocol by dedicating a tune to King George V with the words: “This one’s for you, Rex.” Even more shocking was the song he dedicated to the monarch: “(I’ll be Glad When You’re Dead) You Rascal You.” The King responded by giving Armstrong a gold-plated trumpet.

At that same juncture, the hard-boiled style was starting to influence British sensibilities, as demonstrated by the 1930s thrillers of Graham Greene or the films of Alfred Hitchcock. The American way was now a model for movie directors, just as it was for singers and writers.

Why did the world find this American way of expression so compelling? In a perceptive 1937 essay, Malcolm Cowley captured the reasons why “during the last 10 years Hemingway has been imitated more widely than any other American or British author.” Cowley noted that the new American style “has freed many writers—not only novelists but poets and essayists and simple reporters—from a burden of erudition and affectation that they thought was part of the writer’s equipment. It has encouraged them to write as simply as possible about the things they really feel, instead of the things they think that other people think they ought to feel.”