The word 勒索 is formed by combining two characters, each contributing a core action to create a unified concept. 勒 (lè) originally depicts reining in a horse with a bridle, conveying the sense of coercion, pressure, or restraint. 索 (suǒ) means to demand, seek, or exact something, like pressing for payment. When paired, they sequentially depict the act of first applying pressure or constraint (勒) and then following it with a demand (索), vividly forming the comprehensive idea of "extortion" or "blackmail", using threats to compel someone to hand over what is demanded.