reflux (n.)youdaoicibaDictYouDict[reflux 词源字典]
early 15c., "a flowing back (of the sea, etc.)," from Medieval Latin refluxus, from Latin re- "back, again" (see re-) + fluxus "a flowing" (see flux). Digestive sense is recorded from 1937.[reflux etymology, reflux origin, 英语词源]