The word "杀手" is formed by directly combining two conceptual ideas: the first character "杀" means "to kill", representing the action or function, and the second character "手" means "hand", but here it metaphorically extends to mean a "person" who performs that specific action or role. Therefore, the term is constructed by merging the concept of killing with the concept of a person who does it, resulting in the meaning "killer" or "assassin". It is a straightforward, compound idea where the sum of the parts creates the whole identity of the person.