Did people just call it "The World War", was it called "World War I" because they were expecting another one, or was it referred to as something else?
To post an answer I gave earlier:
The FAQs section has a number of answers related to this question.
According to Hew Strachan, in his work The First World War, Part One: To Arms!, whereas the British and the French largely dubbed WWI 'The Great War', it was the Germans that referred to it as Weltkrieg or 'World War'. This could be seen as a result of how the war played out: for Britain and France, the campaigns in Africa and the Middle East formed secondary considerations in Allied war aims, first and foremost of which was the defeat of Germany and it's Allies on the continent. For Germany on the other hand, the war quickly became one of Germany and it's Allies assailed by armies and resources from much of the world, while efforts to undermine the Allied war efforts embraced a 'global escalation' of the conflict: sending Lenin to Russia in 1917, supporting the Easter Rising in Ireland in 1916, encouraging Turkey to enter the war and the Sultan's declaration of Jihad against the Entente, supporting the Hindu and Muslim Conspiracies in India, sending agents to Afghanistan, Unrestricted Submarine Warfare, and acts of state-sponsored terrorism and sabotage in the United States.