Meaning

noun a widespread outbreak of an infectious disease; many people are infected at the same time

adjective (especially of medicine) of disease or anything resembling a disease; attacking or affecting many individuals in a community or a population simultaneously

originFrom French épidémique, from épidémie, from Medieval Latin epidēmia, reanalysis of plural Late Latin epidēmia, from Ancient Greek ἐπιδήμιος (epidḗmios), from ἐπί (epí, “upon”) + δῆμος (dêmos, “people”). By surface analysis, epi- (“on”) + demic (“of the people”).

Etymology from Wiktionary, CC BY-SA 3.0