Red Herring

The popular story is that escaping prisoners, or fox hunters trying to spoil a hunt, would drag a smelly smoked ("red") herring across their trail to throw pursuing dogs off the scent. It's a vivid image, but historians of fox hunting have found no real evidence of it being used that way. The actual source seems more mundane: a 1686 hunting manual by Nicholas Cox recommended dragging a dead cat or fox to lay an artificial scent trail for training young hunting horses and hounds, and suggested a strong-smelling red herring as a substitute if a cat or fox wasn't available. By the 19th century, that training method had been misremembered as a deliberate trick to fool the hounds, and the figurative sense of "red herring" as a deceptive distraction was born from the misunderstanding.