Earlier quoted context omitted.
Couldn't it also have been called "First World War" because it was the first war where fighting happened - over multiple continents - with huge number of countries participating - at the same time - as part of the same conflict
Arguably, that honor goes to the Seven Years' War, which saw significant fighting both in Europe and in North America. The French Revolutionary Wars/Napoleonic Wars were equally grand in scale, and conducted at a time when the "world" for all practical purposes included only European powers--all of the major ones got involved in those conflicts at one point or another; even the newly-independent US got peripherally i…
The United States, Canada, Japan, New Zealand, and Australia all entered the war.
There were significant theaters of the war in Africa and the Middle East.
China was initially neutral in WWI but did eventually declare support for the Entente and sent 140,000 laborers to Europe. [1]
Brazil entered the war after losing ships to German U boats. [2]
Over a million Indian troops participated. [3]
Thailand, New Guinea, and Samoa were involved [4]
And I’m just scratching the surface. The very worst fighting was concentrated in the industrial meat grinders of the front lines in Europe but there was significant participation from all corners of the earth. It earned the name “World War.”
1. https://en.m.wikipedia.org/wiki/China_during_World_War_I
2. https://en.m.wikipedia.org/wiki/Brazil_during_World_War_I
3. https://en.m.wikipedia.org/wiki/Indian_Army_during_World_War...
4. https://en.m.wikipedia.org/wiki/Asian_and_Pacific_theatre_of...