What Does Foo Mean?

The word foo as slang, can be used as an expression of loathe or disgust. It is also a sample name assigned to a temporary file or program.  The word was used along with the word "bar" to make foobar or FUBAR, which was a derogatory insulting term.

The term foo fighter was used by Allied aircraft pilots in the World War II to imply the occurrence of UFOs (Unidentified Flying Objects) or an uncanny aerial experience like flashy lights in the sky. The foo fighters were understood by the allied armies as enemy aircrafts or aerial spies implanted by the axis powers. The ironical thing was that these unidentified objects never seemed to cause harm to anybody. Foo Fighters is also the name of the band formed by Dave Grohl in the year 1995, the band member from Nirvana.  Foo-foo is the name of the poodle owned by Dennis' foe, Walter the Softy, in the famous comic Dennis the Menace.