1757, "an epidemic disease, a temporary prevalence of a disease throughout a community," from epidemic (adj.); earlier epideme (see epidemy). An Old English noun for this (persisting in Middle English) was man-cwealm.

c. 1600, "common to or affecting a whole people," originally and usually, though not etymologically, in reference to diseases, from French épidémique, from épidemié "an epidemic disease," from Medieval Latin epidemia, from Greek epidemia "a stay in a place; prevalence of an epidemic disease" (especially the plague), from epi "among, upon" (see epi-) + dēmos "people, district" (see demotic). Also see -ic.

"study of epidemics, science of epidemic diseases," 1850, from Greek epidemios, literally "among the people, of one's countrymen at home" (see epidemic) + -logy. Related: Epidemiological; epidemiologist.

"an epidemic disease," especially the plague, late 15c., ipedemye, impedyme, from Old French ypidime (12c., Modern French épidémie), from Late Latin epidemia (see epidemic (adj.)).

animal equivalent of epidemic, 1748, from French épizootique, from épizootie, irregularly formed from Greek epi "on, upon" (see epi-) + zōon "animal" (from PIE root *gwei- "to live"). As an adjective from 1790.

of diseases, "incident to a whole people or region," 1660s, from Late Latin pandemus, from Greek pandemos "pertaining to all people; public, common," from pan- "all" (see pan-) + dēmos "people" (see demotic). Modeled on epidemic; OED reports that it is "Distinguished from epidemic, which may connote limitation to a smaller area." The noun, "a pandemic disease," is recorded by 1853, from the adjective. Related: Pandemia.

*dā-, Proto-Indo-European root meaning "to divide."

It forms all or part of: betide; daimon; Damocles; deal (v.); deal (n.1) "part, portion;" demagogue; demiurge; democracy; demography; demon; demotic; dole; endemic; epidemic; eudaemonic; geodesic; geodesy; ordeal; pandemic; pandemonium; tidal; tide (n.) "rise and fall of the sea;" tidings; tidy; time; zeitgeist.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dati "cuts, divides;" Greek dēmos "people, land," perhaps literally "division of society," daiesthai "to divide;" Old Irish dam "troop, company;" Old English tid "point or portion of time," German Zeit "time."

c. 1300, "any infectious or contagious disease, fatal epidemic," from Old French pestilence "plague, epidemic" (12c.) and directly from Latin pestilentia "a plague, an unwholesome atmosphere," noun of condition from pestilentem (nominative pestilens) "infected, unwholesome, noxious," from pestis "deadly disease, plague" (see pest).

Also in Middle English "wickedness, evil, sin, a vice, that which is morally pestilential."

"epidemic influenza," 1776, probably from French grippe "influenza," originally "seizure," verbal noun from gripper "to grasp, hook," from Frankish or another Germanic source, from Proto-Germanic *gripanan (see grip (v.), gripe (v.)). Supposedly in reference to constriction of the throat felt by sufferers; the word spread through European languages after the influenza epidemic during the Russian occupation of Prussia in the Seven Years' War (c. 1760), and Russian chirpu, said to be imitative of the sound of the cough, is sometimes said to be the origin or inspiration for the word.

"febrile epidemic disease of the tropics," 1828, from West Indian Spanish dengue, from an African source, perhaps Swahili dinga "seizure, cramp," with form influenced by Spanish dengue "prudery" (perhaps because sufferers walk stiffly and erect due to the painful joints which characterize the disease). The disease is from East Africa and was introduced into the West Indies in 1827.