Where Did the Term “Red Herring” Come From and What Does the Expression Mean?

A “red herring” is a false clue leading detectives off the track during a criminal investigation.

The term comes from a practice once used to train police dogs.

When herring is smoked it becomes red, and when the young dogs were being trained to follow a scent, the trainers tossed smoked fish around to test their ability to follow a trail.

Escaping prisoners learned of the practice and often took red herring along to distract the dogs sent after them.

Misleading evidence is often called a “red herring”.