Where did the term World Series come from?

As early as the 1880s post-season series between league champions were sometimes referred to as the “World’s Championship” or “World’s Series of Games.” When the American League and National League officially agreed to play each other at the end of each season in 1905, the term was used by most sportswriters. It was most often called the “World’s Series,” but the “s” was dropped and by the 1920s the label “World Series” was in place. Almost immediately the series was also called the “Fall Classic.” The first modern World Series was in 1903, but the NL and AL didn’t officially agree (in writing) to play each other every post-season, until 1905.