When did World War II get its name?

Answer 1

The war of 1914-1918 was known as the Great War. In the 1930s, the Great War became known as the First World War, so inevitably the 1939-1945 war became the Second World War.

The name "World War" was used some time 1939. Newspapers and governments in the democratic countries discussed how they could avoid a second world war. In Germany, secret conferences were held to plan for and work out how to start what even they called a second world war.

Answer 2

Because almost every country in the world was fighting, it was a "world war."

The similar European conflict from 1914 to 1919 was called the "Great War" or the "World War," so it was natural to declare the later conflict the "second World War" which is commonly known as World War II (WW2).

Answer 3

The 1914-18 war was originally called the Great War, but it was also referred to as the World War because it involved so many countries.

When the 1939 war began, it too involved many countries around the world so people said it was another world war. That led to the Great War being called the first world war and the 1939-45 war as the second world war. The names became formalized with capital letters, and were also shortened using numbers instead of words; e.g. World War 1 (or I, in Roman numerals) or even WWI.