A quick Google found this:
Origin of the Name "World Series"
"One baseball myth that just won't die is that the "World Series" was named for the New York World newspaper, which supposedly sponsored the earliest contests. It didn't, and it wasn't.
In fact, the postseason series between the AL and NL champs was originally known as the "Championship of the World" or "World's Championship Series." That was shortened through usage to "World's Series" and finally to "World Series."
This usage can be traced through the annual baseball guides. Spalding's Base Ball Guide for 1887 reported the results of the 1886 postseason series between Chicago, champions of the National League, and St. Louis, champions of the American Association, under the heading "The World's Championship." As the editor noted, the two leagues "both entitle their championship contests each season as those for the base ball championship of the United States," so a more grandiose name was required to describe the postseason showdown between the two "champions of the United States."
But the Spalding Guide -- which, after all, was published by one of the world's largest sporting goods companies, with a vested interest in bringing baseball to other lands -- had grander ambitions. By 1890, the Spalding Guide was explaining that "[t]he base ball championship of the United States necessarily includes that of the entire world, though the time will come when Australia will step in as a rival, and after that country will come Great Britain; but all that is for the future."
This didn't happen, but the name "World's Championship Series" stuck. Reporting on the first modern postseason series, the Red Sox-Pirates battle of 1903, the 1904 Reach Guide called it the "World's Championship Series." By 1912, Reach's headline spoke of the "World's Series," while editor Francis Richter's text still referred to the "World's Championship Series." The Reach Guide switched from "World's Series" to "World Series" in 1931, retaining the modern usage through its merger with the Spalding Guide and through its final issue in 1941. The separately-edited Spalding Guide used "World's Series" through 1916, switching to "World Series" in the 1917 edition.
The Spalding-Reach Guide was replaced as Major League Baseball's semi-official annual by the Sporting News Guide, first published in 1942. The Sporting News Guide used "World's Series" from 1942 through 1963, changing to "World Series" in the 1964 edition.
Moreover, the New York World never claimed any connection with postseason baseball. The World was a tabloid much given to flamboyant self-promotion. If it had been involved in any way with sponsoring a championship series, the fact would have been emblazoned across its sports pages for months. I reviewed every issue of the World for the months leading up to the 1903 and 1905 World's Championship Series -- there's not a word suggesting any link between the paper and the series."
Copyright © 2001-02 Doug Pappas. All rights reserved.
Originally published in the Fall 2001 issue of Outside the Lines, the SABR Business of Baseball Committee newsletter.