Why is trolling called trolling?

I thought it was trolls under a bridge waiting to upset the next person. They are cloaked or hidden—not really upstanding or galant beings but upsetting little jerks. 

A lot of Internet or Information Age terms are weird...

I personally hate the term "viral," but as far as the term "trolling" goes I've sorta been on board.

It's just a person acting weird on the Internet... and so they're labeled a "troll," and aptly so IMO. 

Trolls on here get slapped with TOS violations like people in Detroit get slapped with parking tickets.

Think of it like fishing.  Someone is fishing for an emotional reaction and feeding off of that instead of trying to ask an honest question.  That's the thing about the English language, words often mean more than one thing.

Trolls hide under bridges. Internet trolls hide under the bridge of anonymity. Thats how it's been described to me.