A red rag to a bull

Meaning

A deliberate provocation, sure to bring about an adverse reaction.

Origin

In the 17th century, to wave a red rag at someone was merely to chatter with them - 'red rag' was then a slang term for the tongue. This usage is cited in print as early as 1605 and is nicely illustrated in Francis Grose's definition in The Classical Dictionary of the Vulgar Tongue, 1785:

"Shut your potatoe trap, and give your redrag a holiday."

The waving of a cloth rag at an animal to distract it may have been a common practice for centuries, but it wasn't until the 1700s that it was documented in print. The animal in question wasn't, as we might suppose, a bull. The first creature known to be susceptible to rag waving was that most dim-witted of birds, the pheasant. This was cited in Trenchard and Gordon's religious essays, Cato's Letters, 1724:

Foxes are trapann'd [trapped] by Traces, Pheasants by a red Rag, and other Birds by a Whistle; and the same is true of Mankind.

Next come vipers, which were also thought to be adversely affected by red rags, as was recorded in The Times in March 1809:

"Truth to a lawyer was like a red rag to a viper - it extracted his venom."

Bulls come rather a long way down the list of red rag sensitive beings found in early citations. Before them we find turkeys and, not to be left out, Frenchmen - as in Catherine Gore's Memoires of a Peeress, 1837:

"They [the English] have no ardour for gratuitous quarrels; they do not fire up like a turkey-cock or a Frenchman, at sight of a red rag."

It wasn't until 1873 that someone decided that bulls were to be added to the list, when Charlotte Yonge included an allusion in the novel Pillars of the House:

"Jack will do for himself if he tells Wilmet her eyes are violet; it is like a red rag to a bull."

The inclusion of bulls to the list was rather misguided. Bulls don't have the optical equipment to distinguish red from other colours, so the 'red rag to a bull' phrase gives the wrong impression. It is generally accepted that bulls are enraged by the waving of the cloth rather than its colour and that a green rag would work just as well. Personally, I've never been close enough to an annoyed bull for a double-blind trial, so to speak, and that is the way I prefer to keep it.