1884, coined in German physicist Eilhard Wiedemann (1852-1928) from Latin lumen (genitive luminis) "light" (from suffixed form of PIE root *leuk- "light, brightness") + -escence.
Fluorescence and Phosphorescence -- Prof. E. Wiedmann has made a new study of these phenomena. He proposes the general name luminescence for evolutions of light which do not depend on the temperature of the substance concerned. ["Photographic News," April 20, 1888]
The verb luminesce (1896) is a back-formation.