Hooah

Hooah /ˈhuːɑː/ is military slang Originally HOOA used by US Army Airborne in World War II meaning " Head Out Of Ass " and was a spin off of Radio Operators HUA "Heard Understood Acknowledged" as the term spread throughout the Army it became more of a general meaning "anything and everything except 'no'".

Used by soldiers in the U.S. Army, which accounts for the vast majority of the usage of the word.