kidnapper

Concise Oxford English Dictionary © 2008 Oxford University Press:
kidnap/ˈkɪdnap/

▶verb (kidnaps, kidnapping, kidnapped; US also kidnaps, kidnaping, kidnaped) abduct and hold captive, typically to obtain a ransom. ▶noun an instance of kidnapping.

– derivatives
kidnapper noun.

– origin C17: back-form. from kidnapper, from kid1 + sl. nap ‘nab, seize’.