phlogiston

Etymology

From New Latin phlogiston, coined by Georg Ernst Stahl in 1702, from Ancient Greek φλογιστόν (phlogistón), neuter of φλογιστός (phlogistós, “burnt up, inflammable”), from φλογίζω (phlogízō, “to set fire to”), from φλόξ (phlóx, “flame”).

noun

1. (chemistry, historical) The hypothetical fiery principle formerly assumed to be a necessary constituent of combustible bodies and to be given up by them in burning.
   […] air was universally reputed to be a simple or elementary body. It was liable, according to the phlogistians, to vitiation, by the addition to it of phlogiston[…] being more or less phlogisticated, according to the degree of its power to support respiration and combustion. 1810, George Wilson, M.D., F.R.D.E., “General Sketch of Cavendish's Scientific Researches and Discoveries”, in The Life of the Honᵇˡᵉ Henry Cavendish, page 39
   Stahl argued that phlogiston could explain combustion, a central concern of eighteenth-century chemistry. 2006, Philip Ball, The Devil's Doctor, Arrow 2007, page 397