Jerry was a nickname given to World War II German soldiers, the German armed forces, or collectively the entirety of Nazi Germany. Although the nickname was originally created during World War I, it didn't find common use until WWII. Other nicknames used for the German soldiers in WWI and WWII were Fritz, Hun, Kraut, and Boche. Jerry has analogues from different eras such as Tommy (British), Charlie (Vietnamese), and Ivan (Russian). Wikipedia
The definitive Wikipedia entry for Jerry. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Jerry_%28WWII%29