Lifeguard

wiktionary

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life +‎  guard,  Calque of Dutch lijfgarde, where life has the sense of Dutch  lijf(“body”) hence  bodyguard [1]. Compare German Leibgarde(“bodyguard”), Danish livgarde(“bodyguard”), Swedish livgarde(“bodyguard”). Compare also Old English līfweard(“guardian of life”). 

etymonline

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lifeguard (n.)

also life-guard, 1640s, "a British monarch's bodyguard of soldiers," from life (n.) + guard (n.), translating German Leibgarde. Sense of "person paid to watch over bathers" is by 1891.