tin hat

noun2

1. •
   (slang, historical) The steel helmet worn by soldiers during World War I.

   • They could live on jerked goat, the strong black coffee they called 'boiler compound,' and hash cooked in a tin hat. — 2007
2. •
   A tinfoil hat.

   • The New World Order is a term that has often been laughed at, ridiculed and considered as paranoia by tin hat wearing conspiracy theorists in recent history. — 2011