US soldiers in World War 1 were called doughboys. The name is believed to have originated in reference to large round brass buttons worn by American infantrymen which looked like little round doughnuts called doughboys. The term was first used to describe the buttons and then became the common slang for the infantrymen themselves and was especially popular during World War I.
'Sieg Heil' means 'Hail to Victory.'
Also D-Day comes from 'Designated Day' for Operation Overlord, the code name for the Allied invasion of Northern France on June 6, 1944, during World War II.