nadir (n.)youdaoicibaDictYouDict[nadir 词源字典]
late 14c., in astronomical sense, from Medieval Latin nadir, from Arabic nazir "opposite to," in nazir as-samt, literally "opposite direction," from nazir "opposite" + as-samt "road, path" (see zenith). Transferred sense of "lowest point (of anything)" is first recorded 1793.[nadir etymology, nadir origin, 英语词源]