Did You Know?

Adust comes from Latin adustus, the past participle of "adurere" ("to set fire to"), a verb formed from the Latin prefix ad- and the verb "urere" ("to burn"). It entered the English language in the early 15th century as a medical term related to the four bodily humors - black bile, blood, phlegm, and yellow bile - which were believed at the time to determine a person's health and temperament. "Adust" was used to describe a condition of the humors in which they supposedly became heated or combusted. Adust black bile in particular was believed to be a source of melancholy. The association with melancholy gave rise to an adjectival sense of adust meaning "of a gloomy appearance or disposition," but that sense is now considered archaic.