early 15c., in ancient and medieval philosophy, "pure essence, substance of which the heavenly bodies are composed," lit. "fifth essence," from M.Fr. quinte essence (14c.), from M.L. quinta essentia, from L. quinta, fem. of quintus "fifth" + essentia (see essence
of Gk. pempte ousia, the "ether" added by Aristotle to the four known elements (water, earth, fire, air) and said to permeate all things. Its extraction was one of the chief goals of alchemy. Sense of "purest essence" (of a situation, character, etc.) is first recorded 1580s.