sentinel (n.)youdaoicibaDictYouDict[sentinel 词源字典]
1570s, from Middle French sentinelle (16c.), from Italian sentinella "a sentinel." OED says "No convincing etymology of the It. word has been proposed," but perhaps (via a notion of "perceive, watch"), from sentire "to hear," from Latin sentire "feel, perceive by the senses" (see sense (n.)).[sentinel etymology, sentinel origin, 英语词源]