red herring

One possible origin of the idiom was that red herring were used to train dogs to track scents. This was true[1], but the modern meaning of a false trail may have been popularised in a news story by English journalist William Cobbett, c. 1805, in which he claimed that as a boy he used a red herring (a cured and salted herring) to mislead hounds following a trail; the story served as an extended metaphor for the London press, which had earned Cobbett's ire by publishing false news accounts regarding Napoleon.[2] The OED has another possible earlier origin in the legacy of clergyman Jasper Mayne in 1672 when he misled a servant by leaving him "Somewhat that would make him Drink after his Death" in a large trunk. When the trunk was opened, the contents were found to be red herring. [3]

red herring (plural red herrings)

1. A smoke-cured and salt-brined herring strong enough to turn the flesh red; a type of kipper.

   "Up in the morning, and had some red herrings to our breakfast, while my boot-heel was a-mending, by the same token the boy left the hole as big as it was before." (Samuel Pepys diary entry of 28 February 1660)[4]

2. (figuratively) A clue, information, argument etc. that is or is intended to be misleading, diverting attention from the real answer or issue.

• clue
• diversion
• evidence
• wild-goose chase
• decoy
• lead by the nose
• lead someone down the garden path