The word 疯子 is formed by directly combining two characters: the first character, 疯, means "mad" or "insane", representing the core quality or condition. The second character, 子, is a very common nominal suffix that, when attached, transforms the descriptive idea into a noun denoting a person associated with that idea. Thus, the compound literally and conceptually means "a mad person" by fusing the trait with a general personifier.