A red herring is a false clue that leads the search astray. Chase a red herring, it was a red herring, throw in a red herring.
In fiction it is a deliberate device, planted so the reader suspects the wrong person. In argument it names introducing something irrelevant to distract, which is a listed fallacy. The name comes from strongly smoked herring, which turns red and reeks — said to have been dragged across a trail to confuse hounds.
1nounred herringA false clue that leads the search astray.
“The torn letter turned out to be a red herring, and the police wasted weeks on it.”
2nounlogicIntroducing something irrelevant to distract.
“In the debate, his point about the speaker's clothes was a red herring to distract from the real issue.”
A red herring is a herring cured until red and pungent. The figurative sense comes from the story of dragging one across a scent trail.
figurative One possible origin of the idiom was that red herring were used to train dogs to track scents. This was true, but the modern meaning of a false trail may have been popularized 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. 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. soldier An allusion to soldiers' red uniforms; soldier is, reciprocally, a slang term for the fish.
Etymology from Wiktionary, CC BY-SA
Practised in Spying & Secrecy