The word 证件 is formed by combining two characters: 证 (zhèng), which carries the core meaning of "proof", "certificate", or "to prove", and 件 (jiàn), which denotes a general item or piece of something, especially documents. Their combination creates a conceptual unit where 件 categorizes the type of object, and 证 specifies its purpose; thus, the compound logically means "an item that serves as proof", a document or credential.