Red herring

In the mystery novel A Study in Scarlet, the detective Sherlock Holmes examines a clue which is later revealed to be intentionally misleading.

A red herring is something that misleads or distracts from an important question, a relevant argument, or the solving of a mystery or crime. It may be either a logical fallacy or a literary device that leads readers or audiences toward a false conclusion. A red herring may be used intentionally, as in mystery fiction or as part of rhetorical strategies (e.g., in politics), or may be used in argumentation inadvertently.

The expression was popularized in 1807 by the English polemicist William Cobbett, who told a story of having used a strong-smelling smoked herring to divert and distract hounds from chasing a rabbit.