Pictured is the dock plant (rumex obtusifolius), a common but valuable weed native to Europe. If you've ever had the misfortune to be pricked by stinging nettles, the leaf of a dock can be applied to the skin to relieve the pain. The hairs of a nettle prickle deliver acetylcholine acid and seratonin, which burn and irritate the skin, and a histamine, an irritant that encourages you to scratch and deliver the acid further into the skin. The leaves of a dock may be chewed and rubbed along the site; grinding the dock leaf releases antihistamines that soothes the irritation and saliva promotes healing.
The healing property of the dock plant is long established in folklore. The first mention of a dock occurs in Bald's Leechbook in reference to its ability to cleanse the bowels while a doctor attempts to cure a stomach ailment.
"...sume þære readan netlan twigu grene, sume betan oþþe doccan on geswettum wine seoþað..." (II, pg. 218 in Cockayne's). "[For the cleansing of a wamb], some seethe in sweetened wine the twigs of red nettles green, some beets or docks."
Bald was a Saxon doctor, writing during the time of Alfred the Great (925-955 CE). Dock was not easily identified, even in Bald's time, and may have stood for several plants. The translator Thomas Cockayne warned that the rigor of modern botany did not exist in the time of Bald. Dock most often referred to rumex, but may have referred to similar looking plants as well. The historian may recall William Turner's remark in 1562 on common folk, "We have a great manner of dock, which the unlearned take for rhubarb" (Herball).
Because the use of the word "dock" could apply to a small number of plants, this may be why we see dock prescribed for so many medical problems. After Bald, dock is used in a dozen or so healing recipes of the Old and Middle English period for ailments as various as eye pain or stomach illness. Despite dock's appearances in many different potions and antidotes, use of the dock plant began to center around its use against the nettle.
In Troilus and Criseyde, oft regarded as Geoffrey Chaucer's finest work, we see the first reference to dock's use against nettle's bite:
"Thow biddest I shulde love another..and lat Criseyde go!..I wolde nat do so, But kanstow playen raket, to and fro, Nettle in, dok out, now this, now that?" (4.416). "Thou biddest I should love another and let Criseyde go! I would not do so, but canst thou play racket to and fro, nettle in, dock out, now this, now that?"
The meaning here is obscure to the modern reader. Obviously Chaucer's line is rooted in metaphor, but, less clearly, Chaucer is referring to ancient proverb as well. On the surface, the speaker Troilus is rebutting the advice of Pandarus. Pandarus advised that Troilus let Criseyde go, that he will return to fall in love with other women. But Troilus asks Pandarus rhetorically if he has reduced the act of love to a game of racket, loving woman after woman as one hits a weathercock again and again. Chaucer's direct intent with the phrase is to disagree with Pandarus, but this does not explain nettles' relationship with the game of rackets.
To solve this mystery we need to work backward by divining the meaning of "nettle in, dock out." The phrase was probably a charm spoken during the act of applying dock leaf to the site of a nettle sting. The words are recorded in 1851 as part of a larger folk charm, used in the Northumberland area, "Nettle in, dock out; dock in, nettle out." To his wit, the plant historian Roy Vickery found a number of similar charm songs, all recorded in the 19th century. The phrase was evidently repeated during the act of pulling out the nettle's stinger and applying the dock leaf: "in the past, it seems that the accompanying words were as important a part of the procedure as the physical process" (Simpson & Roud 2000).
While the charm was used in seriousness during the remedy of a nettle's prick, it must have gained currency as a phrase in racket as well. For Chaucer to be able to reference the words in passing requires that the audience understood its application, both in the healing process and in the racket game. Thomas Usk, a contemporary of Chaucer's - they worked together in customs under the king - wrote in his Testament of Love, "I have not played raket, 'nettil in, docke out', and with the wethercocke waved." (Note the spelling differences of Usk's from Chaucer). The charm said during the extraction of the nettle became a metaphor for the back-and-forth nature of the game of racket. Thus Chaucer is able to extend this metaphor further, by applying it to the game of love. Love, to Chaucer, is not "to and fro" but a lasting relationship between two people.
Cockayne, Thomas Oswald. Leechdoms, Wortcunning and Starcraft. Longman, Green, Longman, Roberts, and Green. 1866.
Simpson, Jacqueline and Stephen Roud. A Dictionary of English Folklore. Oxford Universty Press. 2000.
Vickery, Roy. "Nettles: Their uses and folklore in the British Isles". Folk Life. Vol. 31, Is. 1. 1992.