The first of Galen’s four fluid humours of the body, αἷμα, blood, was associated with the temperament that came to be known as sanguine, from the equivalent Latin word, sanguis. Sanguis meant the fluid that flows from wounds, the blood that colours the face red, bloodshed, as in battle or sacrifice, life blood or the vital fluid, vigour, vitality, the source of one’s instincts, and kindred or consanguinity.

Latin words that invoked sanguis included sanguiculus and sangunculus, both meaning black pudding, and sanguisuga, a leech. Sanguinalis or herba sanguinarius was a plant that stopped haemorrhage, possibly knotgrass, Polygonum aviculare. Mrs Grieve described it in her Modern Herbal (1931) as having astringent properties, “rendering an infusion of it useful in diarrhoea, bleeding piles, and all haemorrhages.” She also said that “it was formerly employed considerably as a vulnerary and styptic . . . The fresh juice has been found effectual to stay bleeding of the nose, squirted up the nose and applied to the temples.”

In his Botanologia (1710) William Salmon said that “Knotgrass is peculiar against spilling of blood.” To Shakespeare, however, it was a plant that retards growth. In A Midsummer Night’s Dream (1595), Lysander tells Hermia “Get you gone, you dwarfe, You minimus of hindring knot-grasse made, You bead, you acorne.” This is the first recorded use in English of the Latin word “minimus”, which is why it was written in italics in every edition of the plays, from the First Folio until it achieved full English status in Samuel Johnson’s edition of 1765.

In English, sanguine, introduced in the 14^th century, was originally an adjective meaning blood red and a noun meaning a cloth of that colour. Chaucer uses both of these meanings in The Canterbury Tales. In Nevill Coghill’s translation of the Prologue, the Doctor’s robes are described as “blood-red garments, slashed with bluish grey / And lined with taffeta . . . ” (picture). The original reads “In sangwyn and in Pers he clad was al, Lyned with taffata and with sendal.” Pers was a cloth of dark blue or bluish-grey colour and sendal was a thin, rich silken material. We have met taffeta before.

Chaucer also summarises current medical theory when he tells us that the Doctor “knew the cause of everich maladye, Were it of hoot, or coold, or moyste, or drye, And where they engendred, and of what humour.” In “The Knight’s Tale”, Coghill describes Emetrius, the Indian King, as having “rounded lips, his colour bright”, but the original is more specific: “Hise lippes rounde, his colour was sangwyn”. In other words, blood red.

Although “sanguine” could refer to the colour of the face, it was also used to describe one of the four complexions, referring to different combinations of the four humours. It was not until the 16^th century that “complexion” came to refer to the colour, texture, and appearance of the skin, particularly that of the face. When Chaucer says of the Franklin that “Of his complexioun he was sangwyn” he is referring to his temperament, not the colour of his face. A sanguine complexion was a temperament in which the blood predominated. It was associated, not only with a ruddy face, but also with an optimistic, courageous, amorous, passionate, and hot headed disposition. Hotspur’s wife, Lady Percy, describes her husband as “altogether govern’ed by humours” (Henry IV, Part 1, Act III.i.230), and says that “in speech, in gait, In diet, in affections of delight, In military rules, humours of blood, He was the mark and glass, copy and book, That fashioned others” (Henry IV, Part 2, Act II.iii.28).

Since the sanguine temperament is associated with an excess of blood, it might be thought that it should also mean bloody minded, which originally meant bloodthirsty or inclined to bloodshed. However, the modern meaning of perverse, contrary, cantankerous, intransigent, or obstructive emerged only in the 1930s, too late for such an association.

I am inclined to be sanguine that the dispute between the government and the junior doctors will be satisfactorily settled eventually, although my optimism is severely tempered by the observation that some of the participants in the dispute seem to be bloody minded.

Jeffrey Aronson is a clinical pharmacologist, working in the Centre for Evidence Based Medicine in Oxford’s Nuffield Department of Primary Care Health Sciences. He is also president emeritus of the British Pharmacological Society.

Competing interests: None declared.