It was the Germans who first spoke of the war as 'der Weltkrieg', the world war; the British preferred the 'European War' or, later, the 'Great War'.
The term 'world war' originated with the Germans, who referred to it as 'der Weltkrieg', reflecting their perspective on the conflict's global implications. In contrast, the British initially described the war as the 'European War', insinuating a more localized focus. Over time, they shifted towards the moniker 'Great War' as the enormity of the conflict became apparent.
This divergence in terminology highlights differing national narratives and perceptions regarding the scale and impact of the war. While the Germans recognized the global context, the British initially emphasized European affairs before acknowledging the war's worldwide significance.