FED (in all caps) is a common way to refer to the Federal Reserve, as is the Fed. Don't ask me why.
IME its common in two groups of people:
1. American anti-Fed conspiracy theorists, and
2. Non-Americans who see the #1 without understanding the nature and assume its a standard US usage.
My personal exposure is a python method from a quant library called get_FED()
I read ZeroHedge occasionally, and I've never seen it spelled "FED" there. I'm wondering where you find conspiracy theorists who type it like that.
More kooky places than ZH. Which by the way is not as bad as you probably think it is.
"On This “Atom Bomb”- Anniversary, You’re Being Lied To About Hiroshima" was published by ZH. I would say denying that nuclear weapons and nuclear power are hoaxes is a bit off the wall.