The word 坚信 is formed by combining two independent concepts into a single, more potent idea. The first character, 坚 (jiān), conveys solidity, hardness, and steadfastness, like an unyielding rock or resolve. The second, 信 (xìn), represents trust, belief, and faith. Their fusion is not merely additive but metaphorical: it takes the abstract notion of "belief" and imbues it with the tangible, physical quality of being "hard and firm", thereby creating the concept of a "firm belief" or conviction that is resolute and unshakeable.