Last night, the Boston Red Sox completed a four-game sweep of the Colorado Rockies to win the 2007 World Series. The team’s name has been spelled with an “X” since 1907. So why aren’t the “Red Sox” the “Red Socks”? In 2005, Daniel Engber examined how the “X” crept into the monikers of two American League ball clubs. The article is reprinted in full below.

If the Chicago White Sox beat the Astros tonight, they’ll be just one victory away from their first World Series title since 1917. Last season, the Boston Red Sox won their first championship since 1918. Why are these teams “Sox” rather than “Socks”?

They followed the fashion of the times. Many early baseball teams were named after their uniform colors. In the 19th century, there were clubs called the Red Stockings, Brown Stockings, and Blue Stockings. Newspapers like the Chicago Tribune often shortened these nicknames to “Sox.” When Charlie Comiskey founded the American League’s Chicago White Stockings in 1901, the Tribune wasted no time in dubbing them the White Sox. Boston’s AL franchise seems not to have had an official name during its first few years. Reporters called them different names on different days, including the Americans (to distinguish them from Boston’s National League team), the Bostons, the Plymouth Rocks, and the Beaneaters. In late 1907, the club’s owner settled on Red Sox.

Why the love affair with the letter “x”? The formation of the modern baseball leagues coincides, more or less, with a broad movement to simplify English spelling. The father of the movement, Noah Webster, had pushed to create a “national language” a century earlier. Webster wanted to distinguish American English from British English by correcting irregular spellings and eliminating silent letters. Some of Webster’s suggestions took—”jail” for “gaol”—while others haven’t caught on—”groop” for “group.”

Near the turn of the century, advocacy groups like the Spelling Simplification Board pushed for spelling reform with renewed vigor; they argued that millions of dollars were wasted on printing useless letters. The editor of the Chicago Tribune, Joseph Medill, supported the idea. Medill stripped final “e”s from words like “favorite” in the pages of his newspaper and even suggested more wholesale changes that would have made written English look something like e-mail spam. In 1906, Teddy Roosevelt ordered the government printer to adopt some simplified spellings—such as replacing the suffix “-ed” with “-t” at the end of many words—for official correspondence. Congress responded by passing a bill in support of standard orthography later that year.

By the first decade of the 1900s, “sox” was already a common way to shorten “socks.” The “x” version of the word frequently appeared in advertisements for hosiery, for example. And in his 1921 tome The American Language, H.L. Mencken described “sox” as a “vigorous newcomer.” “The White Sox are known to all Americans; the White Socks would seem strange,” he wrote.

The spelling reform movement weakened over the course of the 20th century. But by the time “sox” fell out of fashion, the baseball nicknames were already entrenched in the sports pages and in the hearts of the teams’ fans.

Bonus Explainer: The White Sox and Red Sox weren’t the only early-20th century teams not to have a steady nickname. Interchangeable nicknames were common in old-time baseball. Before becoming universally known as the Yankees, New York’s American League team was also known as the Highlanders, the Invaders, and the Porchclimbers in the early 1900s.

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Explainer thanks Jill Lepore of Harvard University and Ben Zimmer of Rutgers University.