.. How do I get past the troll?

Have you tried talking to him?

He wants a toll.

You should probably ask him what the toll is.

He says he wants something of perceived importance with no real value.

In another words, he wants something blatant yet misleading.

What is that literary device in mystery novels (or adventure games) called?

A red herring.

A herring is a type of fish.

Do you have one?

There's one on the dock behind the kitchen in the SCUMM Bar.

How do I get into the kitchen?

How can I get this herring?

Give the troll the fish.