A big name for a club contest
It is called the World Series because the name grew from older phrases such as “World’s Championship Series”. Those words claimed a grand status for a club competition, rather than describing a tournament between countries.
Think of the name as a very confident label, not a list of everyone invited.
The label came first
The Canadian Baseball Hall of Fame traces “World Champions” language to an 1884 contest. The modern series began in 1903, when Boston faced Pittsburgh.
Doug Pappas’s study of old baseball guides follows the wording from “World’s Championship Series” to “World’s Series”, then “World Series”. Different guides changed at different times; there was no single overnight rename.
The newspaper story
A neat-sounding explanation says the New York World newspaper sponsored the contest and supplied its name. Pappas checked the paper’s coverage before the 1903 and 1905 series and found no evidence of that connection.
A newspaper called World makes a memorable story. It does not make the story true.
What the title settles
Today, it decides Major League Baseball’s champion, between the winners of the American and National Leagues.
So “world” preserves an old ambition. The name tells a story about baseball’s history, rather than promising a place for every country.