Sentinel

google

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late 16th century: from French sentinelle, from Italian sentinella, of unknown origin.

wiktionary

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1570s, from Middle French sentinelle, from Old Italian sentinella (perhaps via a notion of " perceive, watch", compare Italian sentire(“to feel, hear, smell”)), from Latin sentiō(“feel, perceive by the senses”). See sense.

etymonline

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sentinel (n.)

1570s, from 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.)).