Kidnap

google

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late 17th century: back-formation from kidnapper, from kid1 + slang nap ‘nab, seize’.

wiktionary

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From kid +‎ nap(“to nab; to grab”)

etymonline

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kidnap (v.)

1680s, thieves' cant, a compound of kid (n.) "child" and nap (v.) "snatch away," which probably is a variant of nab (v.). Perhaps a back-formation from kidnapper, which is recorded earlier. Originally "to steal children to provide servants and laborers in the American colonies." Related: Kidnapped; kidnapping.