The name Foo Fighters is today most commonly thought of in relation to the rock band. But phrase has a history involving cartoons, UFOs and the Second World War.
The term ‘foo’ in those days was a nonsense word used in popular culture and appeared in the long standing American comic strip Smokey Stover by cartoonist Bill Holman from 1935-1972.
It was a popular cartoon and in the Second World War, images of the characters Smokey Stover were painted on some American aircraft.
Pilots in the war often saw strange lights in the sky that they could describe as literally unidentified flying objects.
These UFOs were seen frequently by pilots, so much that the term foo fighters was borrowed from the cartoon and used to identify them.
History.com – Mysterious UFOs Seen by WWII Airman Still Unexplained
Airspacemag.com – What Were the Mysterious “Foo Fighters” Sighted by WWII Night Flyers?