|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
|an extraordinary or unusual thing, person, or event; an exceptional example or instance.|
|1.||anything that diverts attention from a topic or line of inquiry|
|2.||a herring cured by salting and smoking|
In argument, something designed to divert an opponent's attention from the central issue. If a herring is dragged across a trail that hounds are following, it throws them off the scent.
Something that draws attention away from the central issue, as in Talking about the new plant is a red herring to keep us from learning about downsizing plans. The herring in this expression is red and strong-smelling from being preserved by smoking. The idiom alludes to dragging a smoked herring across a trail to cover up the scent and throw off tracking dogs. [Late 1800s]