foo fighter

 
Pronunciation: /ˈfuː ˌfʌɪtə/

noun

  • an unidentified flying object, originally one of a kind reported by US pilots during the Second World War, usually described as a bright light or ball of fire.

Origin:

1940s: from ‘Where there's foo there's fire’, a nonsense catchphrase from the US Smoky Stover cartoon strip