epidemic: [17] An epidemic is literally something that has an effect ‘among the people’. The word comes from French épidémique, a derivative of the noun épidémie, which goes back via late Latin epidēmia to Greek epidēmíā ‘disease prevalent among the people’. This was a noun use of epidémios, a compound adjective formed from the prefix epí- ‘among’ and demos ‘people’ (source of English democracy). => democracy[epidemic etymology, epidemic origin, 英语词源]