[bc2]

A Foo Fighter was the name of jets or pilots who fought UFO's. Not sure if it was from a comic or a movie but that's where they got the name from.

[Leroy S. Mort]

Close, but not quite:

- From: UFO Report -- Spring 1975 edition -

During WWII, when a series of incomprehensible events suddenly erupted over battle zones from North Africa to Guadalcanal to the Rhineland, hundreds of fliers and infantrymen on both sides of the conflict had occasion to look into the skies at a mystery that has never been explained. Whatever the cause, these weird aerial apparitions, which came to be known as "foo fighters", were enough to make witnesses forget momentarily the life and death concerns of men in combat.

[WashingtonSource]

Went to a website for the Seattle Sound

http://www.kurtcobain.de/

Found this explanation:

the band, named the foo fighters after a world war ii secret force that allegedly researched ufos