A note in John’s Bathroom Reader claims that World War II was so named by Harry Truman - in 1945. And that prior to that, FDR had called it “The War for Survival.”
Doesn’t seem right to me. Nobody called it World War II until it was over (or nearly so)?
Kind of tangential, but I was just listening to a book Alistair Cook wrote during and after the war, and while talking about the period just after it ended, he said journalists were still debating what it should be called. So even if the name had been proposed much earlier, it wasn’t a done deal until after it ended.
In case you haven’t clicked through to any of the links, Time magazine introduced the term “World War II” in its issue of June 12, 1939, three months before the war in Europe began.