More about phlogiston
Phlogiston “a chemical once thought to be released during combustion” is the neuter form of Ancient Greek phlogistós “inflammable, burnt up,” from the verb phlogízein “to set on fire.” Relatives of phlogízein in English include phlegm (from phlégma “flame”) and phlox (from phlóx “a flame-colored plant”). All these words ultimately come from a Proto-Indo-European root roughly meaning “to burn, flash, shine” that appears today in English words containing bl-, fl-, ful-, or phl-, depending on the language of origin. For more descendants in English from this rather productive root, check out our recent Words of the Day effulgent, Phlegethon, and trailblaze. Phlogiston was first recorded in English circa 1730.