Today’s factoid:
The term ‘red herring’ to mean a confusing or deceptive clue originated from methods used to disrupt or sabotage a fox hunt. Red herrings (a dried and smoked herring) had a strong odour which was often used to train dogs to follow scents. By dragging a red herring across the path of a fox, the hounds could become confused and start following the scent trail of the herring.
Source: Worldwidewords.org.