Arnold Groh is not a historian, instead he holds degrees in psychology, literature and linguistics. When I asked him if he could expand on his footnote he said the following:
My father (1913-2014) witnessed the Nazis. When the terms "global",
"globalization" etc. became popular around the turn of the millenia, he said that Hermann Göring liked to use the term "global" a lot. As you know, guys like Göring, Goebbels, Hitler etc. kept giving speeches in front of large audiences that were also broadcast. Thus, the term was popularised.
While the footnote was based on the subjective experience of the author's father there is some evidence that the term "global" was used deliberately in Nazi propaganda.
Back in 1925 Hitler wrote in Mein Kampf (British translation of the unexpurgated edition) that he viewed global domination as a missed opportunity with unclaimed land a requirement for population growth of a nation.
For, as things stand today, vast spaces still lie uncultivated all over the surface of the globe. Those spaces are only waiting for the ploughshare. And it is quite certain that Nature did not set those territories apart as the exclusive pastures of any one nation or race to be held unutilized in reserve for the future. Such land awaits the people who have the strength to acquire it and the diligence to cultivate it.
If a nation confines itself to ‘internal colonization’ while other races are perpetually increasing their territorial annexations all over the globe, that nation will be forced to restrict the numerical growth of its population at a time when the other nations are increasing theirs.
If in its historical development the German people had possessed the unity of herd instinct by which other peoples have so much benefited, then the German Reich would probably be mistress of the globe to-day.
It should be noted that more accurate translations of Mein Kampf could exist and "globe" could be mistranslated as "Earth" but conceptually they are the same thing and reflects how it was read at the time.
It wasn’t until the launch of the war that the threat of the “international Jewry” was created as noted by Jeffrey Herf who wrote in The Jewish Enemy: Nazi Propaganda During World War II and the Holocaust
Though Hitler had long planned to launch the war at a time and place of his choosing, he and his propagandists insisted that the “extermination” of the Jews was a justified response to a war launched against Germany by “international Jewry.”
He then explains that this would have created a global threat:
Radical anti-Semitism rested on the belief that the Jews were a cohesive, politically active subject—that is, a group united on a global scale by racial bonds that transcended any allegiance to nation-states. In the Nazi view, this powerful and autonomous entity, international Jewry, controlled assorted stooges and accomplices who served its evil interests.
According to Wikipedia between 1933 and 1945 Hitler gave a total of 1,525 speeches and I am not able to check them all but I did make use of the Nazi and East German Propaganda Archive from Calvin University. Using Google search I found 15 references of the term "globe" or “global” and the use of it ranges from the threat of "international Jewry" by Joseph Goebbels in 1935 to loose concepts of "global struggles" in 1944
It has been thought out, set afoot and led under the inspiration of the Mammon worship and materialist thought which is incarnated in international Jewry, scattered throughout every country of the globe.
It cannot be ignored that anti-Bolshevism and its related anti-Semitism has significantly increased in all warring nations during the course of this war, particularly over the last six months. That is the result of the length of the war on one hand, but also because of our extraordinarily intensive educational work on the fundamental problems of this global struggle that extends to the whole world.
Without doing original research all I can show is that, conceptually, Hitler had global ambitions and created a global threat. It goes some way to explain the sudden increase in the word "global" from 1940 onwards. Given that the term didn’t appear during WW1 shows that something more is happening than just a reaction to a global war. If we use alternative German words suggested by Google Translate like "Weltweit_INF", "Allumfassend_INF" and "weltumspannend_INF" they all existed before in the 1800s and peaked during WW1 and WW2 but it seems the Third Reich was more directly responsible for “global”.
In the end it might have been that Groh’s father meant “Earth” since that word also increased in usage during the 1940s and Göring certainly used it in his speeches. However there still exists a sudden introduction of the word "global" from the 1940s. If someone can provide a better explanation then I will gladly accept your answer as the solution.