In medieval medicinal practice, four “humors” dictated a patient’s overall health: sanguine (blood), choleric (yellow bile), melancholic (black bile), and phlegmatic (phlegm). Medieval doctors used to describe patients as sanguine if they had flushed skin, and this was considered a sign of good health. While the diagnostic use of humors has long been disproved, the adjective “sanguine” can still be applied to someone with an optimistic outlook (especially in a tough situation). Etymologically, the word comes from the Latin for “of blood.”