Much Ado about Nothing?

ON HADDOCKS AND HERRING.

When is a herring actually a red herring?  It's been driving me crazy that in The 39 Steps, Hitchcock repeatedly references  herring and haddock to the point that I'm still obsessed by it.

I may have solved the mystery. Hitchcock invented the use of a red herring or McGuffin in his movies.

A Red Herring is something in a story that has no relevance to the story, except to make the audience wonder where it might fit into the plot later.

 Sometimes, the audience might not even notice it except as some background item or back-story, but usually it's predominant enough to make the viewer/reader think that it has something to do with solving the puzzle that will be revealed in time.

A McGuffin, explained Hitchcock, comes from a Scottish joke about someone basically telling another to "mind his own business." The first asks the second about the contents in a box or package, and the second explains that it's a McGuffin. "Whats a McGuffin?" "It's a Scottish lion trap" "but there are no lions in Scotland, "Well, then that's not a McGuffin, is it?" In other words - it's none of your business.

In actuality, a "Red Herring" is a real herring fish that, once smoked, gets red in color and has a heavy fishy scent, thus it's presence is obvious to anyone around. Sometimes a Red Herring in a movie is used just for fun, other times it's a serious point in the story's plot. And sometimes it means nothing at all.

Could haddock and herrings be a red herrings after all?