The term foo fighter was used by Allied aircraft pilots in World War II to describe various UFOs or mysterious aerial phenomena seen in the skies over Europe and the Pacific theatre. Contemporary witnesses often assumed that the foo fighters were secret weapons employed by the enemy, and it was not until after the war that it was discovered neither side had anything to do with them. Despite these fears, foo fighters (whatever they might have been) were apparently never reported to have harmed or tried to harm anyone.
Though usually thought of as blobs of light or fire, several different types of reported phenomena were classed as "foo fighters".
There were several other terms used to describe these objects (such as "Kraut fireballs"), but "foo fighter" seems to have been the most popular.
The term is generally thought to have been borrowed from the often surrealist comic strip Smokey Stover. Smokey, a firefighter, was fond of saying "Where there's foo there's fire." (this "foo" may have come from "feu", the French word for "fire", or from Smokey's pronunciation of the word "fuel".) A Big Little Book titled Smokey Stover the Foo Fighter was published in 1938. Foo may have also come from the French word faux meaning, in this case, 'fake'.
In the same vein, "Foo" could be derived from the French "Fou," or "mad."
Some have thought that the term refers to Kung fu ("kong foo") fighting, because of the reported wild, erratic movements of these aerial objects. The term Kung fu was, however, little known in the English language until the late 1960s when it became popular because of the Hong Kong films and the later Kung Fu: before that it was referred to primarily as "Chinese Boxing".
1. interj. Term of disgust. 2. [very common] Used very generally as a sample name for absolutely anything - When `foo' is used in connection with `bar' it has generally traced to the WWII-era Army slang acronym FUBAR (`Fucked Up Beyond All Repair'), later modified to foobar. This change used to be interpreted as a post-war bowdlerization, but it now seems more likely that FUBAR was itself a derivative of `foo' perhaps influenced by German `furchtbar' (terrible) - `foobar' may actually have been the original form. It seems, the word `foo' itself had an immediate prewar history in comic strips and cartoons. The earliest documented uses were in the "Smokey Stover" comic strip published from about 1930 to about 1952. Bill Holman, the author of the strip, filled it with odd jokes and personal contrivances, including other nonsense phrases such as "Notary Sojac" and "1506 nix nix". The word "foo" frequently appeared on license plates of cars, in nonsense sayings in the background of some frames (such as "He who foos last foos best" or "Many smoke but foo men chew"), and Holman had Smokey say "Where there's foo, there's fire". One place "foo" is known to have remained live is in the