period: [14] Period means etymologically ‘going round’. It comes via Old French periode and Latin periodus from Greek períodos, a compound noun formed from the prefix perí- ‘round’ and hódos ‘way’ (source also of English episode, exodus [17], and method). The main sense of the word in modern English, ‘interval of time’ (which first emerged in post-classical Latin), comes from the notion of a ‘repeated cycle of events’ (now more obvious in the derivative periodical [17]). => episode, exodus, method[period etymology, period origin, 英语词源]