A red herring is something that misleads or distracts from a relevant or important issue. It may be either a logical fallacy or a literary device that leads readers or audiences towards a false conclusion. A red herring might be intentionally used, such as in mystery fiction or as part of rhetorical strategies (e.g., in politics), or it could be inadvertently used during argumentation.
The term was popularized in 1807 by English polemicist William Cobbett, who told a story of having used a kipper (a strong-smelling smoked fish) to divert hounds from chasing a hare.
“When I was a boy, we used, in order to draw oft’ the harriers from the trail of a hare that we had set down as our own private property, get to her haunt early in the morning, and drag a red-herring, tied to a string, four or five miles over hedges and ditches, across fields and through coppices, till we got to a point, whence we were pretty sure the hunters would not return to the spot where they had thrown off; and, though I would, by no means, be understood, as comparing the editors and proprietors of the London daily press to animals half so sagacious and so faithful as hounds, I cannot help thinking, that, in the case to which we are referring, they must have been misled, at first, by some political deceiver.”
–William Cobbett, February 14, 1807, Cobbett’s Political Register, Volume XI