The word "按钮" is formed by combining two characters that each contribute a core aspect of the final concept. The first character, "按" (àn), means "to press down", directly conveying the primary action. The second character, "钮" (niǔ), originally means a knob, dial, or protrusion, the physical object that is manipulated. Together, they create a single, unified idea: a protrusion or fixture designed to be pressed, perfectly capturing the functional essence of a mechanical or electronic button.