Were they know as world wars during the conflict or is this a label history has given them?
Pretty much right away.
The famous German biologist Ernst Haeckel referred to the war as the First World War in September 1914.
In 1920 Charles à Court Repington a former British officer and then a war correspondent published a book called "The first world war, 1914-1918" which is the earliest book I've heard of to use the term.
https://archive.org/details/firstworldwar19100repi
QI did a bit on it and discussed that he referred to the war as the First World War in 1918 not long before it ended when talking to an American officer.