IPA: /ˈkɪd.næp/
KK: /ˈkɪdˌnæp/
To take someone away by force or threat, often to demand money for their return.
The police worked hard to rescue the child who had been kidnapped.
Past: kidnapped
Past Participle: kidnapped
Kidnap is formed from "kid" (from Middle English *kidde*, meaning a young goat or child) and "nap" (from the Old English *napian*, meaning to seize or take). The word originally referred to the act of seizing a child.
Think of 'kid' as a young child being 'seized' or 'taken' — that's why kidnap means to take a child.