φλεγματικός

Phlegmatic derives from Greek phlegma (flame, inflammation, mucus), from phlegein (to burn). The connection between fire and mucus seems contradictory, but it follows ancient medical logic: inflammation produced swelling, swelling produced fluid, and the body's cold, wet fluid was phlegm. The word traveled from burning to its opposite. Hippocrates and Galen built the four-humor theory around blood, phlegm, yellow bile, and black bile. Each humor corresponded to a temperament.

The phlegmatic person, in humoral theory, had an excess of phlegm — the cold, wet humor associated with water and winter. This made them calm, slow, passive, and difficult to anger. The phlegmatic temperament was not praised. Galen and his followers considered it a sign of sluggishness, laziness, and emotional flatness. The ideal was a balance of all four humors. An excess of any one was a disease, not a personality.

The word entered English in the fourteenth century through medieval medical texts. For centuries, 'phlegmatic' was a clinical diagnosis. A phlegmatic patient needed warming, drying remedies — pepper, wine, exercise — to burn off the excess cold moisture. The word was medical before it was psychological, and psychological before it was complimentary.

Modern English has reversed the word's valence. 'Phlegmatic' now suggests admirable calm — the British stiff upper lip, the unflappable leader, the person who stays cool under pressure. The trait that Galen considered a disorder is now considered a virtue. The mucus that named it has been forgotten entirely.