[tcuoohjohn]

It is a reference to tin foil helmets. There is a phenomenon among very whacky conspiracy theorists that also leads them to believe that the government or aliens are sending " gamma" or other rays into their heads to prevent them from discovering " the real truth". The prevention measure is a cleverly crafted tin foil helmet to deflect the incoming rays.

There you have it...

[jamaksin]

Thank you.

I made the connection with a "tin can" and "tin foil" as the earlier term for aluminum wrapping "foil."

Geometry must factor in there somewhere - particularly with "gamma" rays.

Thank you again.